Resist composition and method of forming resist pattern

ABSTRACT

A resist composition containing a resin component (A1) having a constitutional unit derived from a compound represented by General Formula (a01-1). In the formula, W 01  represents a polymerizable group-containing group, C t  represents a tertiary carbon atom, and X t  represents a group that forms a monocyclic or polycyclic alicyclic group together with C t , Ra 1  to Ra 3  represents a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra 1  to Ra 3  are bonded to each other to form an aliphatic ring, not all of Ra 1  to Ra 3  are hydrogen atoms, n represents 0 or 1

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a resist composition and a method of forming a resist pattern.

Priority is claimed on Japanese Patent Application No. 2020-117209, filed on Jul. 7, 2020, the content of which is incorporated herein by reference.

Description of Related Art

In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have led to a rapid progress in the field of pattern miniaturization. Typically, these miniaturization techniques involve shortening the wavelength (increasing the energy) of the light source for exposure.

Resist materials for use with these types of light sources for exposure require lithography characteristics such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of light sources for exposure.

As a resist material that satisfies these requirements, a chemical amplification-type resist composition which contains a base material component exhibiting changed solubility in a developing solution under action of acid, and an acid generator component which generates an acid upon exposure has been conventionally used.

In the chemical amplification-type resist composition, a resin having a plurality of constitutional units is generally used for improving the lithography characteristics and the like.

For example, Patent Document 1 describes a resist composition that employs a specific polymer compound having high acid dissociation performance to improve reactivity with an acid, and the like.

CITATION LIST Patent Document

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2017-3919

SUMMARY OF THE INVENTION

With the further progress of lithography technology and the miniaturization of a resist pattern, for example, it is aimed to form a fine pattern of several tens of nanometers in lithography by EUV and EB. As the resist pattern size becomes smaller as described above, a resist composition is required to have high sensitivity and good lithography characteristics with respect to a light source for exposure.

However, in a case of trying to increase the reactivity of a protecting group of a polymer compound in order to increase the sensitivity, where the polymer compound is conventionally used as a base material component, the physical properties of the polymer compound also change significantly, whereby the lithography characteristics may deteriorate. As a result, it has been difficult to achieve both high sensitivity and good lithography characteristics. In particular, in terms of the lithography characteristics, a resist composition having a wide exposure margin is required from the viewpoint of being able to stably form a fine pattern.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a resist composition, which has higher sensitivity and good lithography characteristics (particularly, a wide exposure margin), and a method of forming a resist pattern by using the resist composition.

In order to achieve the above-described object, the present invention employs the following configurations.

That is, the first aspect according to the present invention is a resist composition which generates an acid upon exposure and exhibiting changed solubility in a developing solution under action of acid. The resist composition contains a resin component (A1) exhibiting changed solubility in a developing solution under action of acid. The resin component (A1) has a constitutional unit (a01) derived from a compound represented by General Formula (a01-1).

[In the formula, W⁰¹ represents a polymerizable group-containing group. C^(t) represents a tertiary carbon atom, and X^(t) represents a group that forms a monocyclic or polycyclic alicyclic group together with C^(t). Part or all of hydrogen atoms which the monocyclic or polycyclic alicyclic group has may be substituted with a substituent. Ra¹ to Ra³ each independently represents a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form an aliphatic ring. However, not all of Ra¹ to Ra³ are hydrogen atoms. n represents 0 or 1.]

The second aspect according to the present invention is a method of forming a resist pattern, including a step of forming a resist film on a support using the resist composition according to the first aspect, a step of exposing the resist film, and a step of developing the exposed resist film to form a resist pattern.

According to the present invention, it is possible to provide a resist composition, which has higher sensitivity and good lithography characteristics (particularly, a wide exposure margin), and a method of forming a resist pattern by using the resist composition.

DETAILED DESCRIPTION OF THE INVENTION

In the present specification and the scope of the present claims, the term “aliphatic” is a relative concept used with respect to the term “aromatic” and defines a group or compound that has no aromaticity.

The term “alkyl group” includes a monovalent saturated hydrocarbon group that is linear, branched, or cyclic, unless otherwise specified. The same applies to the alkyl group of an alkoxy group.

The term “alkylene group” includes a divalent saturated hydrocarbon group that is linear, branched, or cyclic, unless otherwise specified.

Examples of the “halogen atom” include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

The term “constitutional unit” means a monomer unit (monomeric unit) that constitutes to the formation of a polymer compound (a resin, a polymer, or a copolymer).

In a case where “may have a substituent” is described, both of a case where a hydrogen atom (—H) is substituted with a monovalent group and a case where a methylene group (—CH₂—) is substituted with a divalent group are included.

The term “exposure” is used as a general concept that includes irradiation with any form of radiation.

The term “acid-decomposable group” indicates a group in which at least a part of a bond in the structure of the acid-decomposable group can be cleaved by action of acid.

Examples of the acid-decomposable group having a polarity which is increased by action of acid include groups which are decomposed by action of acid to generate a polar group.

Examples of the polar group include a carboxy group, a hydroxyl group, an amino group, and a sulfo group (—SO₃H).

More specific examples of the acid-decomposable group include a group in which the above-described polar group has been protected with an acid-dissociable group (for example, a group in which a hydrogen atom of the OH-containing polar group has been protected with an acid-dissociable group).

The “acid-dissociable group” indicates any one of (i) a group in which a bond between the acid-dissociable group and an atom adjacent to the acid-dissociable group can be cleaved by action of acid; and (ii) a group in which a part of bonds are cleaved by action of acid, and then a decarboxylation reaction occurs, thereby cleaving the bond between the acid-dissociable group and the atom adjacent to the acid-dissociable group.”

It is necessary that the acid-dissociable group that constitutes the acid-decomposable group be a group that exhibits a lower polarity than the polar group generated by the dissociation of the acid-dissociable group. Thus, in a case where the acid-dissociable group is dissociated by action of acid, a polar group exhibiting a higher polarity than the acid-dissociable group is generated, thereby increasing the polarity. As a result, the polarity of the entire component (A1) is increased. By the increase in the polarity, the solubility in a developing solution relatively changes. The solubility in a developing solution is increased in a case where the developing solution is an alkali developing solution, whereas the solubility in a developing solution is decreased in a case where the developing solution is an organic developing solution.

The “base material component” is an organic compound having a film-forming ability. The organic compounds used as the base material component are roughly classified into a non-polymer and a polymer. As the non-polymer, those having a molecular weight of 500 or more and less than 4,000 are usually used. Hereinafter, a “low-molecular-weight compound” refers to a non-polymer having a molecular weight of 500 or more and less than 4,000. As the polymer, those having a molecular weight of 1,000 or more are usually used. Hereinafter, a “resin”, a “polymer compound”, or a “polymer” refers to a polymer having a molecular weight of 1,000 or more. As the molecular weight of the polymer, a polystyrene-equivalent weight-average molecular weight determined by gel permeation chromatography (GPC) is used.

A “constitutional unit derived from” means a constitutional unit that is formed by the cleavage of a multiple bond between carbon atoms, for example, an ethylenic double bond.

In the “acrylic acid ester”, the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent. The substituent (Ra^(αx)) that is substituted for the hydrogen atom bonded to the carbon atom at the α-position is an atom other than a hydrogen atom or a group. Further, itaconic acid diester in which the substituent (Ra^(αx)) is substituted with a substituent having an ester bond or α-hydroxyacryl ester in which the substituent (Ra^(αx)) is substituted with a hydroxyalkyl group or a group in which a hydroxyl group thereof is modified can be mentioned as an acrylic acid ester. A carbon atom at the α-position of acrylic acid ester indicates the carbon atom bonded to the carbonyl group of acrylic acid, unless otherwise specified.

Hereinafter, acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position is substituted with a substituent is also referred to as an α-substituted acrylic acid ester”.

The term “derivative” includes a compound in which the hydrogen atom at the α-position of the object compound has been substituted with another substituent such as an alkyl group or a halogenated alkyl group; and derivatives thereof. Examples of the derivatives thereof include a derivative in which the hydrogen atom of the hydroxyl group of the object compound in which the hydrogen atom at the α-position may be substituted with a substituent is substituted with an organic group; and a derivative in which a substituent other than a hydroxyl group is bonded to the object compound in which the hydrogen atom at the α-position may be substituted with a substituent. The α-position refers to the first carbon atom adjacent to the functional group unless otherwise specified.

Examples of the substituent that is substituted for the hydrogen atom at the α-position of hydroxystyrene include the same group as R^(αx).

In the present specification and the scope of the present claims, asymmetric carbon atoms may be present, and thus enantiomers or diastereomers may be present depending on the structures of the chemical formula. In that case, these isomers are represented by one chemical formula. These isomers may be used alone or in the form of a mixture.

(Resist Composition)

The resist composition according to the present embodiment is a resist composition which generates an acid upon exposure and exhibiting changed solubility in a developing solution under action of acid.

In a case where a resist film is formed using the resist composition according to the present embodiment and the formed resist film is subjected to selective exposure, an acid is generated at the exposed portion of the resist film, and the generated acid acts on the component (A) to change the solubility of the component (A) in a developing solution, whereas the solubility of the component (A) in a developing solution is not changed at the unexposed portion, thereby which generates the difference in solubility in the developing solution between the exposed portion and the unexposed portion of the resist film.

The resist composition according to the present embodiment may be a positive-tone resist composition or a negative-tone resist composition.

Further, in the formation of a resist pattern, the resist composition according to the present embodiment can be applied to an alkali developing process using an alkali developing solution in the developing treatment, or a solvent developing process using an organic developing solution in the developing treatment.

That is, the resist composition according to the present embodiment is a “positive-tone resist composition for an alkali developing process” that forms a positive-tone resist pattern in an alkali developing process and is a “negative-tone resist composition for a solvent developing process” that forms a negative-tone resist pattern in a solvent developing process.

<Component (A)>

In the resist composition according to the present embodiment, the component (A) contains a resin component (A1) (hereinafter, also referred to as a “component (A1)”) exhibiting changed solubility in a developing solution under action of acid, and the resin component (A1) has a constitutional unit (a01) derived from a compound represented by General Formula (a01-1).

As the component (A), at least the component (A1) is used, and at least one of another polymer compound and another low-molecular-weight compound may be used in combination with the component (A1).

In the resist composition according to the present embodiment, the component (A) may be used alone or in a combination of two or more kinds thereof.

In regard to component (A1)

The component (A1) has a constitutional unit (a01).

<<Constitutional Unit (a01)>>

The constitutional unit (a01) is a constitutional unit derived from a compound represented by General Formula (a01-1).

[In the formula, W⁰¹ represents a polymerizable group-containing group. C^(t) represents a tertiary carbon atom, and X^(t) represents a group that forms a monocyclic or polycyclic alicyclic group together with C^(t). Part or all of hydrogen atoms which the monocyclic or polycyclic alicyclic group has may be substituted with a substituent. Ra¹ to Ra³ each independently represents a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form an aliphatic ring. However, not all of Ra¹ to Ra³ are hydrogen atoms. n represents 0 or 1.]

In General Formula (a01-1), W⁰¹ represents a polymerizable group-containing group.

The “polymerizable group” as W⁰¹ is a group that enables a compound having the polymerizable group to be polymerized by radical polymerization or the like, and includes a group containing a multiple bond between carbon atoms, such as an ethylenic double bond.

In the constitutional unit (a01), the multiple bonds in the polymerizable group are cleaved to form a main chain.

Examples of the polymerizable group as W⁰¹ include a vinyl group, an allyl group, acryloyl group, a methacryloyl group, a fluorovinyl group, a difluorovinyl group, a trifluorovinyl group, a difluorotrifluoromethylvinyl group, a trifluoroallyl group, a perfluoroallyl group, a trifluoromethylacryloyl group, a nonylfluorobutylacryloyl group, a vinyl ether group, a fluorine-containing vinyl ether group, an allyl ether group, a fluorine-containing allyl ether group, a styryl group, and a vinylnaphthyl group, a fluorine-containing styryl group, a fluorine-containing vinylnaphthyl group, a norbornyl group, a fluorine-containing norbornyl group, and a silyl group.

The “polymerizable group-containing group” as W⁰¹ may be a group composed of only a polymerizable group, or a group composed of a polymerizable group and a group other than the polymerizable group. Examples of the group other than the polymerizable group include a divalent hydrocarbon group which may have a substituent and a divalent linking group containing a hetero atom.

Divalent hydrocarbon group which may have substituent:

In a case where the group other than the polymerizable group represents a divalent hydrocarbon group which may have a substituent, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group as a Group Other than the Polymerizable Group

The aliphatic hydrocarbon group indicates a hydrocarbon group that has no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated.

Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, and an aliphatic hydrocarbon group containing a ring in the structure thereof.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms.

The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4 carbon atoms, and most preferably 3 carbon atoms.

The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylalkylene groups, for example, alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The linear or branched aliphatic hydrocarbon group may have a substituent or may not have a substituent. Examples of the substituent include a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms, which has been substituted with a fluorine atom, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing Ring in Structure Thereof

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include a cyclic aliphatic hydrocarbon group which may have a substituent containing a hetero atom in the ring structure thereof (a group in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), a group in which the cyclic aliphatic hydrocarbon group is bonded to the terminal of a linear or branched aliphatic hydrocarbon group, and a group in which the cyclic aliphatic hydrocarbon group is interposed in a linear or branched aliphatic hydrocarbon group. Examples of the linear or branched aliphatic hydrocarbon group include the same groups as those described above.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbon atoms and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which two hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane is preferably a group having 7 to 12 carbon atoms. Specific examples of the polycyclic alicyclic hydrocarbon group include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may have or may not have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group as the substituent include groups in which part or all of hydrogen atoms in the above-described alkyl groups have been substituted with the above-described halogen atoms.

In the cyclic aliphatic hydrocarbon group, a part of carbon atoms constituting the ring structure thereof may be substituted with a substituent containing a hetero atom. The substituent containing a hetero atom is preferably —O—, —C(═O)—O—, —S—, —S(═O)₂—, or —S(═O)₂—O—.

Aromatic Hydrocarbon Group as Group Other than the Polymerizable Group

The aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.

The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons, and may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Here, the number of carbon atoms in a substituent is not included in the number of carbon atoms. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and an aromatic heterocyclic ring in which a part of carbon atoms constituting the above-described aromatic hydrocarbon ring have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocyclic ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group in which two hydrogen atoms have been removed from the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring (an arylene group or a heteroarylene group); a group in which two hydrogen atoms have been removed from an aromatic compound having two or more aromatic rings (for example, biphenyl or fluorene); and a group in which one hydrogen atom of a group (an aryl group or a heteroaryl group) obtained by removing one hydrogen atom from the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring has been substituted with an alkylene group (for example, a group in which one hydrogen atom has been further removed from an aryl group in arylalkyl groups such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group bonded to the aryl group or the heteroaryl group preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

With respect to the aromatic hydrocarbon group, the hydrogen atom which the aromatic hydrocarbon group has may be substituted with a substituent. For example, the hydrogen atom bonded to the aromatic ring in the aromatic hydrocarbon group may be substituted with a substituent. Examples of substituents include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.

Examples of the alkoxy group, the halogen atom, and the halogenated alkyl group, as the substituent, include the same groups as those exemplified as the substituent that is substituted for a hydrogen atom which the cyclic aliphatic hydrocarbon group has.

Divalent Linking Group Containing Hetero Atom

In a case where the group other than the polymerizable group represents a divalent linking group containing a hetero atom, preferred examples of the linking group include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O— —C(═O)—NH—, —NH—, —NH—C(═NH)— (H may be substituted with a substituent such as an alkyl group, an acyl group, or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and a group represented by General Formula: —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²² each independently represent a divalent hydrocarbon group which may have a substituent, 0 represents an oxygen atom, and m″ represents an integer in a range of 0 to 3].

In a case where the divalent linking group containing a hetero atom is —C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH—, or —NH—C(═NH)—, H may be substituted with a substituent such as an alkyl group, an acyl group, or the like. The substituent (an alkyl group, an acyl group, or the like) preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 5 carbon atoms.

In General Formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²—, and —Y²¹—S(═O)₂—O—Y²²—, Y²¹, and Y²² each independently represent a divalent hydrocarbon group which may have a substituent. Examples of the divalent hydrocarbon group include the same groups as those (described as the divalent hydrocarbon group which may have a substituent) described in the explanation of the above-described divalent linking group.

Y²¹ is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, still more preferably a linear alkylene group having 1 to 5 carbon atoms, and particularly preferably a methylene group or an ethylene group.

Y²² is preferably a linear or branched aliphatic hydrocarbon group and more preferably a methylene group, an ethylene group, or an alkylmethylene group. The alkyl group in the alkylmethylene group is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.

In the group represented by Formula —[Y²¹—C(═O)—O]_(m″)—Y²²—, m″ represents an integer in a range of 0 to 3, preferably an integer in a range of 0 to 2, more preferably 0 or 1, and particularly preferably 1. In other words, it is particularly preferable that the group represented by Formula —[Y²¹—C(═O)—O]_(m″)—Y²²— represent a group represented by Formula —Y²¹—C(═O)—O—Y²²—. Among them, a group represented by Formula —(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ represents an integer in a range of 1 to 10, preferably an integer in a range of 1 to 8, more preferably an integer in a range of 1 to 5, still more preferably 1 or 2, and most preferably 1. b′ represents an integer in a range of 1 to 10, preferably an integer in a range of 1 to 8, more preferably an integer in a range of 1 to 5, still more preferably 1 or 2, and most preferably 1.

Suitable examples of the polymerizable group-containing group as W⁰¹ include a group represented by a chemical formula: C(R^(X11))(R^(X12))═C(R^(X13))—Ya^(x0).

In the chemical formula, R^(X11), R^(X12), and R^(X13) each represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, and Ya^(x0) represents a single bond or a divalent linking group.

The alkyl group having 1 to 5 carbon atoms as R^(X11), R^(X12), and R^(X13) is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. The halogenated alkyl group having 1 to 5 carbon atoms is a group in which part or all of hydrogen atoms in the alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

Among these, R^(X11) and R^(X12) are each preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and in terms of industrial availability, a hydrogen atom or a methyl group is more preferable.

In addition, R^(X13) is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and in terms of industrial availability, a hydrogen atom or a methyl group is more preferable.

The divalent linking group as Ya^(x0) is not particularly limited, and suitable examples thereof include a divalent hydrocarbon group which may have a substituent and a divalent linking group having a hetero atom, each of which is the same as that described above.

Among the above, Ya^(x0) is preferably an ester bond [—C(═O)—O— or —O—C(═O)—], an ether bond (—O—), a linear or branched alkylene group, an aromatic hydrocarbon group, or a combination thereof, or a single bond. Among these, Ya^(x0) is more preferably a group composed of a combination of an ester bond [—C(═O)—O— or —O—C(═O)—] and a linear alkylene group or a single bond. Specific examples of the group composed of a combination of an ester bond [—C(═O)—O—, —OC(═O)—] and a linear alkylene group include —C(═O)—O—CH₂—.

In General Formula (a01-1), X^(t) represents a group that forms a monocyclic or polycyclic alicyclic group together with C^(t). The polycyclic alicyclic group may be a condensed polycyclic hydrocarbon group in which an aromatic ring is condensed with the alicyclic group. In addition, in the monocyclic or polycyclic alicyclic group, a part of carbon atoms constituting the ring structure thereof may be substituted with a substituent containing a hetero atom. Examples of the substituent containing a hetero atom include —O—, —C(═O)—O—, —S—, —S(═O)₂—, and —S(═O)₂—O—.

The monocyclic alicyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane or a monocycloalkene. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The monocycloalkene preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentene and cyclohexene.

The polycyclic alicyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane or a polycycloalkene. The polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. In addition, the polycycloalkene is preferably a group having 7 to 12 carbon atoms. Specific examples thereof include adamantene, norbornene, isobornene, tricyclodecene, and tetracyclododecene.

Examples of the condensed polycyclic hydrocarbon group in which an aromatic ring is condensed with an alicyclic group include a group in which one hydrogen atom has been removed from an aliphatic ring of a bicyclic compound such as tetrahydronaphthalene or indane.

In the monocyclic or polycyclic alicyclic group that is formed by X^(t) and C^(t), part or all of hydrogen atoms which the monocyclic or polycyclic alicyclic group have may be substituted with a substituent. Examples of the substituent include, —R^(P1), —R^(P2)—O—R^(P1), —R^(P2)—CO—R^(P1), —R^(P2)—CO—OR^(P1), —R^(P2)—O—CO—R^(P1), —R^(P2)—OH, —R^(P2)—CN, and —R^(P2)—COOH (hereinafter, these substituents are also collectively referred to as “Ra⁰⁶”).

Here, R^(P1) represents a monovalent chain-like saturated hydrocarbon group having 1 to 10 carbon atoms, a monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms. In addition, R^(P2) represents a single bond, a divalent chain-like saturated hydrocarbon group having 1 to 10 carbon atoms, a divalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 30 carbon atoms. However, part or all of hydrogen atoms included in the chain-like saturated hydrocarbon group, the aliphatic cyclic saturated hydrocarbon group, and the aromatic hydrocarbon group of R^(P1) and R^(P2) may be substituted with a fluorine atom. In the aliphatic cyclic hydrocarbon group, one or more of the above-described substituents may be included as a single kind, or one or more of the above-described substituents may be included as a plurality of kinds.

Examples of the monovalent chain-like saturated hydrocarbon group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group.

Examples of the monovalent aliphatic cyclic saturated hydrocarbon group having 3 to 20 carbon atoms include monocyclic aliphatic saturated hydrocarbon groups such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and cyclododecyl group; and polycyclic aliphatic saturated hydrocarbon groups such as a bicyclo[2.2.2]octanyl group, a tricyclo[5.2.1.02,6]decanyl group, a tricyclo [3.3.1.13,7]decanyl group, a tetracyclo[6.2.1.13,6.02,7] dodecanyl group, and an adamantyl group.

Examples of the monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms include a group in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene, biphenyl, fluorene, naphthalene, anthracene, or phenanthrene.

Among the above, the substituent is preferably —RP, more preferably a monovalent chain-like saturated hydrocarbon group having 1 to 10 carbon atoms, still more preferably a monovalent chain-like saturated hydrocarbon group having 1 to 5 carbon atoms, and particularly preferably a methyl group or an ethyl group.

Among the above, in General Formula (a01-1), X^(t) is preferably a group that forms a monocyclic alicyclic group together with C^(t). The monocyclic alicyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, or a cyclooctyl group is more preferable, and a cyclopentyl group or a cyclohexyl group is still more preferable.

In General Formula (a01-1), Ra¹ to Ra³ each independently represents a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form an aliphatic ring. However, not all of Ra¹ to Ra³ are hydrogen atoms.

Examples of the substituent which the hydrocarbon group having 1 to 10 carbon atoms may have include Ra⁰⁶ and the like.

The hydrocarbon group having 1 to 10 carbon atoms which may have the above substituent may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.

Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, and an aliphatic hydrocarbon group containing a ring in the structure thereof. The linear or branched aliphatic hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group; however, it is preferably a saturated hydrocarbon group.

The linear or branched aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly more preferably 1 or 2 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include a cyclic aliphatic hydrocarbon group which may have a substituent containing a hetero atom in the ring structure thereof (a group in which one hydrogen atoms have been removed from an aliphatic hydrocarbon ring), a group in which the cyclic aliphatic hydrocarbon group is bonded to the terminal of a linear or branched aliphatic hydrocarbon group, and a group in which the cyclic aliphatic hydrocarbon group is interposed in a linear or branched aliphatic hydrocarbon group. Examples of the linear or branched aliphatic hydrocarbon group include the same groups as those described above.

The cyclic aliphatic hydrocarbon group may be a polycyclic aliphatic hydrocarbon group or a monocyclic aliphatic hydrocarbon group; however, it is preferably a monocyclic aliphatic hydrocarbon group.

The cyclic aliphatic hydrocarbon group preferably has 3 to 10 carbon atoms and more preferably 5 to 8 carbon atoms. Specific examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, and a cyclododecyl group.

Examples of the aromatic hydrocarbon group include a group in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene or naphthalene.

In a case where two or more of Ra¹ to Ra³ are bonded to each other to form an aliphatic ring, the aliphatic ring may be a polycyclic ring or a monocyclic ring.

Further, in the aliphatic ring, a part of carbon atoms constituting the ring structure thereof may be substituted with a substituent containing a hetero atom. Examples of the substituent containing a hetero atom include —O—, —C(═O)—O—, —S—, —S(═O)₂—, and —S(═O)₂—O—.

The monocyclic aliphatic ring that is formed by bonding two or more Ra¹ to Ra³ to each other preferably has 3 to 10 carbon atoms and more preferably 5 to 8 carbon atoms.

Specifically, the monocyclic aliphatic ring is preferably cyclopentene or cyclohexene.

The polycyclic aliphatic ring formed by bonding two or more Ra¹ to Ra³ to each other preferably has 7 to 12 carbon atoms.

Specific examples of the polycyclic aliphatic ring include adamantene, norbornene, isobornene, tricyclodecene, and tetracyclododecene.

The aliphatic ring formed by bonding two or more Ra¹ to Ra³ to each other may have a substituent. Examples of the substituent include Ra⁰⁶.

Among the above, in a case where two or more of Ra¹ to Ra³ in General Formula (a01-1) are not bonded to each other to form an aliphatic ring, Ra¹ to Ra³ each independently preferably a linear or branched aliphatic hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, more preferably a linear or branched saturated aliphatic hydrocarbon group having 1 to 5 carbon atoms, which may have a substituent, or a hydrogen atom, and still more preferably a methyl group, an ethyl group, an n-butyl group, or a hydrogen atom. However, not all of Ra¹ to Ra³ are hydrogen atoms.

Further, in this case, from the viewpoint of further improving sensitivity, at least one of Ra² and Ra³ is preferably a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent. That is, the constitutional unit (a01) in which Ra¹ is a hydrogen atom, and one of Ra² and Ra³ is a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, is more preferable than the constitutional unit (a01) in which Ra¹ is a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, and Ra² and Ra³ is a hydrogen atom.

In a case where two or more of Ra¹ to Ra³ in General Formula (a01-1) are bonded to each other to form an aliphatic ring, the aliphatic ring is preferably a monocyclic aliphatic ring and more preferably cyclopentene or cyclohexene.

That is, in General Formula (a01-1), it is preferable that Ra¹ to Ra³ be each independently a linear or branched aliphatic hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form a monocyclic aliphatic ring, more preferable that Ra¹ to Ra³ are each independently a linear or branched saturated aliphatic hydrocarbon group having 1 to 5 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form a monocyclic aliphatic ring, and still more preferable that Ra¹ to Ra³ be each independently a methyl group, an ethyl group, an n-butyl group, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form cyclopentene or cyclohexene. However, not all of Ra¹ to Ra³ are hydrogen atoms.

Further, in General Formula (a01-1), the total number of carbon atoms of Ra¹ to Ra³ is preferably in a range of 1 to 5 and more preferably 1 or 2.

In General Formula (a01-1), n represent 0 or 1 and preferably 0.

Among the above, the constitutional unit (a01) is more preferably a constitutional unit represented by General Formula (a01-1-1).

[In the formula, R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Va⁰¹ represents a divalent hydrocarbon group which may have an ether bond. n_(a01) represents an integer in a range of 0 to 2. C^(t) represents a tertiary carbon atom, and Xa^(t) represents a group that forms a monocyclic alicyclic group together with C^(t). Ra¹ to Ra³ each independently represents a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form an aliphatic ring. However, not all of Ra¹ to Ra³ are hydrogen atoms. n represents 0 or 1.]

In General Formula (a01-1-1), the alkyl group having 1 to 5 carbon atoms as R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. The halogenated alkyl group having 1 to 5 carbon atoms is a group in which part or all of hydrogen atoms in the alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

As R, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms is preferable, and a hydrogen atom or a methyl group is most preferable in terms of industrial availability.

In General Formula (a01-1-1), Va⁰¹ represents a divalent hydrocarbon group which may have an ether bond, and the divalent hydrocarbon group is the same as the divalent hydrocarbon group exemplified in the explanation of W⁰¹ in General Formula (a01-1). Among the above, a linear or branched aliphatic hydrocarbon group is preferable, a linear alkylene group is more preferable, and a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], or a pentamethylene group [—(CH₂)₅—] is still more preferable.

In General Formula (a01-1-1), n_(a01) represents an integer in a range of 0 to 2, preferably 0 or 1, and more preferably 0.

In General Formula (a01-1-1), Xa^(t) is a group that forms a monocyclic alicyclic group together with C^(t), and examples of the monocyclic alicyclic group include the same group as the monocyclic alicyclic group that is formed by X^(t) in General Formula (a01-1) together with C^(t).

Ra¹ to Ra³ and n in General Formula (a01-1-1) are the same as Ra¹ to Ra³ and n in General Formulae (a01-1).

Specific examples of the constitutional unit (a01) are shown below. In each of the formulae shown below, R^(α) represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

Among the above, the constitutional unit (a01) is preferably at least one selected from the group consisting of constitutional units each represented by General Formulae (a01-1a-1) to (a01-1a-13), more preferably at least one selected from the group consisting of constitutional units each represented by General Formulae (a01-1a-1) to (a01-1a-11), and still more preferably at least one selected from the group consisting of constitutional units each represented by General Formulae (a01-1a-1) to (a01-1a-5) and (a01-1a-8) to (a01-1a-11).

The constitutional unit (a01) that the component (A1) has may be one kind or may be two or more kinds.

The proportion of the constitutional unit (a01) in the component (A1) is preferably in a range of 20% to 80% by mole, more preferably in a range of 30% to 70% by mole, and still more preferably in a range of 35% to 65% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a01) is set within the preferred range described above, the efficiency of the deprotection reaction and the solubility of the developing solution can be appropriately ensured, and thus the effects according to the present invention can be more easily obtained.

<<Other Constitutional Units>>

The component (A1) may have other constitutional units as necessary in addition to the constitutional unit (a01).

Examples of the other constitutional units include a constitutional unit (a1) containing an acid-decomposable group having a polarity which is increased by action of acid (provided that a constitutional unit corresponding to the constitutional unit (a01) is excluded); a constitutional unit (a2) containing a lactone-containing cyclic group, a —SO₂—-containing cyclic group, or a carbonate-containing cyclic group (provided that a constitutional unit corresponding to the constitutional unit (a01) or the constitutional unit (a1) is excluded); a constitutional unit (a3) containing a polar group-containing aliphatic hydrocarbon group (provided that a constitutional unit corresponding to the constitutional unit (a01), the constitutional unit (a1), or the constitutional unit (a2) is excluded); a constitutional unit (a10) represented by General Formula (a10-1) described later; a constitutional unit (a8) derived from a compound represented by General Formula (a8-1) described later; a constitutional unit (a4) containing an acid non-dissociable aliphatic cyclic group; and a constitutional unit (st) derived from styrene or a styrene derivative.

In regard to constitutional unit (a1):

The component (A1) may further have a constitutional unit (a1) in addition to the constitutional unit (a01).

The constitutional unit (a1) is a constitutional unit (provided that a constitutional unit corresponding to the constitutional unit (a01) is excluded) containing an acid-decomposable group having a polarity which is increased by action of acid.

Examples of the acid-dissociable group that constitutes the acid-decomposable group are the same as those which have been proposed so far as acid-dissociable groups for the base resin for a chemical amplification-type resist composition.

Specific examples of acid-dissociable groups of the base resin proposed for a chemical amplification-type resist composition contains an “acetal-type acid-dissociable group”, a “tertiary alkyl ester-type acid-dissociable group”, and a “tertiary alkyloxycarbonyl acid-dissociable group” described below.

Acetal-Type Acid-Dissociable Group:

Examples of the acid-dissociable group for protecting a carboxy group or a hydroxyl group as a polar group include the acid-dissociable group represented by General Formula (a1-r-1) shown below (hereinafter, also referred to as an “acetal-type acid-dissociable group”).

[In the formula, Ra′¹ to Ra′² represent hydrogen atoms or alkyl groups. Ra′³ represents a hydrocarbon group, and Ra′³ may be bonded to Ra′¹ or Ra′² to form a ring.]

In General Formula (a1-r-1), it is preferable that at least one of Ra′¹ and Ra′² represent a hydrogen atom and more preferable that both of Ra′¹ and Ra′² represent hydrogen atoms.

In a case where Ra′¹ or Ra′² represents an alkyl group, the alkyl group is preferably an alkyl group having 1 to 5 carbon atoms. Specific examples thereof preferably include a linear or branched alkyl group. More specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. Among these, a methyl group or an ethyl group is preferable, and a methyl group is particularly preferable.

In General Formula (a1-r-1), examples of the hydrocarbon group as Ra′³ include a linear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group has preferably 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 or 2 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group has preferably 3 to 10 carbon atoms and more preferably 3 to 5 carbon atoms. Specific examples thereof include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group. Among these, an isopropyl group is preferable.

In a case where Ra′³ represents a cyclic hydrocarbon group, the cyclic hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group and may be a polycyclic group or a monocyclic group.

The aliphatic hydrocarbon group which is a monocyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.

The aliphatic hydrocarbon group which is a polycyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane. The polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

In a case where the cyclic hydrocarbon group as Ra′³ is an aromatic hydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring.

The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons, and may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms.

Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and an aromatic heterocyclic ring in which a part of carbon atoms constituting the above-described aromatic hydrocarbon ring have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocyclic ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group as Ra′³ include a group in which one hydrogen atom has been removed from the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring (an aryl group or a heteroaryl group); a group in which one hydrogen atom has been removed from an aromatic compound having two or more aromatic rings (for example, biphenyl or fluorene); and a group in which one hydrogen atom of the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring has been substituted with an alkylene group (for example, an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group bonded to the aromatic hydrocarbon ring or aromatic heterocyclic ring preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

The cyclic hydrocarbon group as Ra′³ may have a substituent. Examples of this substituent include Ra^(x5) described above.

In a case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, the cyclic group is preferably a 4- to 7-membered ring, and more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

Tertiary Alkyl Ester-Type Acid-Dissociable Group:

Among the above polar groups, examples of the acid-dissociable group for protecting the carboxy group include the acid-dissociable group represented by General Formula (a1-r-2) shown below.

Among the acid-dissociable groups represented by General Formula (a1-r-2), for convenience, a group which is constituted of alkyl groups is referred to as a “tertiary alkyl ester-type acid-dissociable group”.

[In the formula, Ra′⁴ to Ra′⁶ each represents a hydrocarbon group, and Ra′⁵ and Ra′⁶ may be bonded to each other to form a ring.]

Examples of the hydrocarbon group as Ra′⁴ include a linear or branched alkyl group, a chain-like or cyclic alkenyl group, and a cyclic hydrocarbon group.

Examples of the linear or branched alkyl group and the cyclic hydrocarbon group (the aliphatic hydrocarbon group which is a monocyclic group, the aliphatic hydrocarbon group which is a polycyclic group, or the aromatic hydrocarbon group) as Ra′⁴ include the same groups as Ra′³ described above.

The chain-like or cyclic alkenyl group as Ra′⁴ is preferably an alkenyl group having 2 to 10 carbon atoms.

Examples of the hydrocarbon group as Ra′⁵ or Ra′⁶ include the same group as Ra′³ described above.

In a case where Ra′⁵ to Ra′⁶ are bonded to each other to form a ring, groups represented by General Formula (a1-r2-1), General Formula (a1-r2-2), and General Formula (a1-r2-3) can be suitably mentioned.

On the other hand, in a case where Ra′⁴ to Ra′⁶ are not bonded to each other and represent an independent hydrocarbon group, a group represented by General Formula (a1-r2-4) can be suitably mentioned.

[In General Formula (a1-r2-1), Ra′¹⁰ represents a linear or branched alkyl group having 1 to 12 carbon atoms, a part of which may be substituted with a halogen atom or a hetero atom-containing group. Ra′¹¹ represents a group that forms an aliphatic cyclic group together with a carbon atom to which Ra′¹⁰ is bonded. In General Formula (a1-r2-2), Ya represents a carbon atom. Xa is a group that forms a cyclic hydrocarbon group together with Ya. Part or all of the hydrogen atoms which the cyclic hydrocarbon group has may be substituted. In General Formula (a1-r2-3), Yaa represents a carbon atom. Xaa is a group that forms an aliphatic cyclic group together with Yaa. Ra¹⁰⁴ represents an aromatic hydrocarbon group which may have a substituent. In General Formula (a1-r2-4), Ra′¹² and Ra′¹³ each independently represent a monovalent chain-like saturated hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom. Part or all of the hydrogen atoms which the chain-like saturated hydrocarbon group has may be substituted. Ra′14 represents a hydrocarbon group which may have a substituent. * represents a bonding site.]

In General Formula (a1-r2-1), Ra′¹⁰ represents a linear or branched alkyl group having 1 to 12 carbon atoms, a part of which may be substituted with a halogen atom or a hetero atom-containing group.

The linear alkyl group as Ra′¹⁰ has 1 to 12 carbon atoms, and preferably has 1 to 10 carbon atoms and particularly preferably 1 to 5 carbon atoms.

Examples of the branched alkyl group as Ra′¹⁰ include the same group as Ra′³.

A part of the alkyl group as Ra′¹⁰ may be substituted with a halogen atom or a hetero atom-containing group. For example, a part of hydrogen atoms constituting the alkyl group may be substituted with a halogen atom or a hetero atom-containing group. Further, a part of carbon atoms (such as methylene group) constituting the alkyl group may be substituted with a hetero atom-containing group.

Examples of the hetero atom mentioned here include an oxygen atom, a sulfur atom, and a nitrogen atom. Examples of the hetero atom-containing group include (—O—), —C(═O)—O—, —O—C(═O)—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—, —S—, —S(═O)₂—, and —S(═O)₂—O—.

In General Formula (a1-r2-1), Ra′¹¹ (a group that forms an aliphatic cyclic group together with a carbon atom to which Ra′¹⁰ is bonded) is preferably the group mentioned as the aliphatic hydrocarbon group (the alicyclic hydrocarbon group) which is a monocyclic group or a polycyclic group as Ra′³ in General Formula (a1-r-1). Among them, a monocyclic alicyclic hydrocarbon group is preferable, specifically, a cyclopentyl group or a cyclohexyl group is more preferable, and a cyclopentyl group is still more preferable.

In General Formula (a1-r2-2), examples of the cyclic hydrocarbon group that is formed by Xa together with Ya include a group in which one or more hydrogen atoms are further removed from a cyclic monovalent hydrocarbon group (an aliphatic hydrocarbon group) as Ra′³ in General Formula (a1-r-1).

The cyclic hydrocarbon group that is formed by Xa together with Ya may have a substituent. Examples of this substituent include the same group as the substituent which the cyclic hydrocarbon group as Ra′³ may have.

In General Formula (a1-r2-3), an aliphatic cyclic group that is formed by Xaa together with Yaa is preferably the group mentioned as the aliphatic hydrocarbon group which is a monocyclic group or a polycyclic group as Ra′³ in General Formula (a1-r-1).

In General Formula (a1-r2-3), Examples of the aromatic hydrocarbon group as Ra¹⁰⁴ include a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 5 to 30 carbon atoms. Among them, Ra¹⁰⁴ l is preferably a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, anthracene, or phenanthrene, still more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, or anthracene, particularly preferably a group in which one or more hydrogen atoms have been removed from benzene or naphthalene, and most preferably a group in which one or more hydrogen atoms have been removed from benzene.

Examples of the substituent which Ra¹⁰⁴ in General Formula (a1-r2-3) may have include a methyl group, an ethyl group, propyl group, a hydroxy group, a carboxy group, a halogen atom, an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and the like), and an alkyloxycarbonyl group.

In General Formula (a1-r2-4), Ra′¹² and Ra′¹³ each independently represent a monovalent chain-like saturated hydrocarbon group having 1 to 10 carbon atoms or a hydrogen atom.

Among them, Ra′¹² and Ra′¹³ are preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, still more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

In a case where the chain-like saturated hydrocarbon groups represented by Ra′¹² and Ra′¹³ are substituted, examples of the substituent include the same group as Ra^(x5) described above.

In General Formula (a1-r2-4), Ra′¹⁴ represents a hydrocarbon group which may have a substituent. Examples of the hydrocarbon group as Ra′¹⁴ include a linear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group as Ra′¹⁴ has preferably 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 or 2 carbon atoms. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group as Ra′¹⁴ has preferably 3 to 10 carbon atoms and more preferably 3 to 5 carbon atoms. Specific examples thereof include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group a 1,1-diethylpropyl group, and a 2,2-dimethylbutyl group. Among these, an isopropyl group is preferable.

In a case where Ra′¹⁴ represents a cyclic hydrocarbon group, the cyclic hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group and may be a polycyclic group or a monocyclic group.

The aliphatic hydrocarbon group which is a monocyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.

The aliphatic hydrocarbon group which is a polycyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane. The polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

Examples of the aromatic hydrocarbon group as Ra′¹⁴ include the same group as the aromatic hydrocarbon group as Ra¹⁰⁴. Among them, Ra′¹⁴ is preferably a group in which one or more hydrogen atoms have been removed from an aromatic hydrocarbon ring having 6 to 15 carbon atoms, more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, anthracene, or phenanthrene, still more preferably a group in which one or more hydrogen atoms have been removed from benzene, naphthalene, or anthracene, particularly preferably a group in which one or more hydrogen atoms have been removed from naphthalene or anthracene, and most preferably a group in which one or more hydrogen atoms have been removed from naphthalene.

Examples of the substituent which Ra′¹⁴ may have include the same group as the substituent which Ra¹⁰⁴ may have.

In a case where Ra′¹⁴ in General Formula (a1-r2-4) is a naphthyl group, the position at which the tertiary carbon atom in General Formula (a1-r2-4) is bonded is any of the 1-position and the 2-position of the naphthyl group.

In a case where Ra′¹⁴ in Formula (a1-r2-4) is an anthryl group, the position at which the tertiary carbon atom in Formula (a1-r2-4) is bonded is any of the 1-position, the 2-position, and 9-position of the anthryl group.

Specific examples of the group represented by General Formula (a1-r2-1) are shown below.

Specific examples of the group represented by General Formula (a1-r2-2) are shown below.

Specific examples of the group represented by Formula (a1-r2-3) are shown below.

Specific examples of the group represented by General Formula (a1-r2-4) are shown below.

Tertiary Alkyloxycarbonyl Acid-Dissociable Group:

Among the polar groups, examples of the acid-dissociable group for protecting a hydroxyl group include an acid-dissociable group (hereinafter, for convenience, also referred to as a “tertiary alkyloxycarbonyl acid-dissociable group”) represented by General Formula (a1-r-3) shown below.

[In the formula, Ra′⁷ to Ra′⁹ each represents an alkyl group.]

In General Formula (a1-r-3), Ra′⁷ to Ra′⁹ are each preferably an alkyl group having 1 to 5 carbon atoms and more preferably an alkyl group having 1 to 3 carbon atoms.

Further, the total number of carbon atoms in each of the alkyl groups is preferably in a range of 3 to 7, more preferably in a range of 3 to 5, and most preferably 3 or 4.

Examples of the constitutional unit (a1) include a constitutional unit derived from acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent; a constitutional unit derived from acrylamide; a constitutional unit in which at least a part of hydrogen atoms in a hydroxyl group of a constitutional unit derived from hydroxystyrene or a hydroxystyrene derivative are protected by the substituent including an acid-decomposable group; and a constitutional unit in which at least a part of hydrogen atoms in —C(═O)—OH of a constitutional unit derived from vinylbenzoic acid or a vinylbenzoic acid derivative are protected by the substituent including an acid-decomposable group.

Specific examples of the constitutional unit (a1) are shown below. In each of the formulae shown below, R^(α) represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

The constitutional unit (a1) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) contains the constitutional unit (a1), the proportion of the constitutional unit (a1) in the component (A1) is preferably in a range of 5% to 50% by mole and more preferably in a range of 5% to 40% by mole with respect to the total (100% by mole) of all constitutional units constituting the component (A1).

In regard to constitutional unit (a2):

The component (A1) may further have, as necessary, a constitutional unit (a2) containing a lactone-containing cyclic group, a —SO₂—-containing cyclic group, or a carbonate-containing cyclic group.

In a case where the component (A1) is used for forming a resist film, the lactone-containing cyclic group, the —SO₂—-containing cyclic group, or the carbonate-containing cyclic group in the constitutional unit (a2) is effective for improving the adhesiveness of the resist film to the substrate. Further, due to having the constitutional unit (a2), lithography characteristics can be improved, for example, by the effects obtained by appropriately adjusting the acid diffusion length, increasing the adhesiveness of the resist film to the substrate, and appropriately adjusting the solubility during development.

The term “lactone-containing cyclic group” indicates a cyclic group that contains a ring (lactone ring) containing a —O—C(═O)— in the ring skeleton. In a case where the lactone ring is counted as the first ring and the group contains only the lactone ring, the group is referred to as a monocyclic group. Further, in a case where the group has other ring structures, the group is referred to as a polycyclic group regardless of the structures. The lactone-containing cyclic group may be a monocyclic group or a polycyclic group.

The lactone-containing cyclic group for the constitutional unit (a2) is not particularly limited, and any lactone-containing cyclic group may be used. Specific examples thereof include groups each represented by General Formulae (a2-r-1) to (a2-r-7) shown below.

[In the formulae, each Ra′²¹ independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyano group; R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂—-containing cyclic group; A″ represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 5 carbon atoms, which may contain an oxygen atom (—O—) or a sulfur atom (—S—); and n′ represents an integer in a range of 0 to 2, and m′ is 0 or 1.]

In General Formulae (a2-r-1) to (a2-r-7), the alkyl group as Ra′²¹ is preferably an alkyl group having 1 to 6 carbon atoms. The alkyl group is preferably a linear alkyl group or a branched alkyl group. Specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, and a hexyl group. Among these, a methyl group or ethyl group is preferable, and a methyl group is particularly preferable.

The alkoxy group as Ra′²¹ is preferably an alkoxy group having 1 to 6 carbon atoms. Further, the alkoxy group is preferably a linear or branched alkoxy group. Specific examples of the alkoxy groups include a group that is formed by linking the above-described alkyl group mentioned as the alkyl group represented by Ra′²¹ to an oxygen atom (—O—).

The halogen atom as Ra′²¹ is preferably a fluorine atom.

Examples of the halogenated alkyl group as Ra′²¹ include groups in which part or all of hydrogen atoms in the above-described alkyl group as Ra′²¹ have been substituted with the above-described halogen atoms. The halogenated alkyl group is preferably a fluorinated alkyl group and particularly preferably a perfluoroalkyl group.

In —COOR″ and —OC(═O)R″ as Ra′²¹, R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂—-containing cyclic group.

The alkyl group as R″ may be linear, branched, or cyclic, and preferably has 1 to 15 carbon atoms.

In a case where R″ represents a linear or branched alkyl group, it is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, and particularly preferably a methyl group or an ethyl group.

In a case where R″ represents a cyclic alkyl group, the cyclic alkyl group preferably has 3 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and particularly preferably 5 to 10 carbon atoms. Specific examples thereof include a group in which one or more hydrogen atoms have been removed from a monocycloalkane, which may or may not be substituted with a fluorine atom or a fluorinated alkyl group; and a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as bicycloalkane, tricycloalkane, or tetracycloalkane. More specific examples thereof include a group in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane or cyclohexane; and a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.

Examples of the lactone-containing cyclic group as R″ include the same groups as those each represented by General Formulae (a2-r-1) to (a2-r-7).

The carbonate-containing cyclic group as R″ has the same definition as that for the carbonate-containing cyclic group described below. Specific examples of the carbonate-containing cyclic group include groups each represented by General Formulae (ax3-r-1) to (ax3-r-3).

The —SO₂—-containing cyclic group as R″ has the same definition as that for the —SO₂—-containing cyclic group described below. Specific examples thereof include groups each represented by General Formulae (a5-r-1) to (a5-r-4).

The hydroxyalkyl group as Ra′²¹ preferably has 1 to 6 carbon atoms, and specific examples thereof include a group in which at least one hydrogen atom in the alkyl group as Ra′²¹ has been substituted with a hydroxyl group.

In General Formulae (a2-r-2), (a2-r-3) and (a2-r-5), as the alkylene group having 1 to 5 carbon atoms as A″, a linear or branched alkylene group is preferable, and examples thereof include a methylene group, an ethylene group, an n-propylene group, and an isopropylene group. Specific examples of the alkylene groups that contain an oxygen atom or a sulfur atom include groups in which —O— or —S— is interposed in the terminal of the alkylene group or between the carbon atoms of the alkylene group, and examples thereof include —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, and —CH₂—S—CH₂—. A″ is preferably an alkylene group having 1 to 5 carbon atoms or —O—, more preferably an alkylene group having 1 to 5 carbon atoms, and most preferably a methylene group.

Specific examples of the groups each represented by General Formulae (a2-r-1) to (a2-r-7) are shown below.

The “—SO₂—-containing cyclic group” indicates a cyclic group having a ring containing —SO₂— in the ring skeleton thereof. Specifically, the —SO₂—-containing cyclic group is a cyclic group in which the sulfur atom (S) in —SO₂— forms a part of the ring skeleton of the cyclic group. In a case where the ring containing —SO₂— in the ring skeleton thereof is counted as the first ring and the group contains only the ring, the group is referred to as a monocyclic group. Further, in a case where the group has other ring structures, the group is referred to as a polycyclic group regardless of the structures. The —SO₂—-containing cyclic group may be a monocyclic group or a polycyclic group. As the —SO₂—-containing cyclic group, a cyclic group containing —O—SO₂— in the ring skeleton thereof, in other words, a cyclic group containing a sultone ring in which —O—S— in the —O—SO₂— group forms a part of the ring skeleton thereof is particularly preferable.

More specific examples of the —SO₂—-containing cyclic group include groups each represented by General Formulae (a5-r-1) to (a5-r-4) shown below.

[In the formulae, each Ra′⁵¹ independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyano group; R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂—-containing cyclic group; A″ represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 5 carbon atoms, which may contain an oxygen atom or a sulfur atom; and n′ represents an integer in a range of 0 to 2.]

In General Formulae (a5-r-1) and (a5-r-2), A″ has the same definition as that for A″ in General Formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, the alkoxy group, the halogen atom, the halogenated alkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl group, as Ra′⁵¹, include the same groups as those described in the explanation of Ra′²¹ in General Formulae (a2-r-1) to (a2-r-7).

Specific examples of the groups each represented by General Formulae (a5-r-1) to (a5-r-4) are shown below. In the formulae shown below, “Ac” represents an acetyl group.

The “carbonate-containing cyclic group” indicates a cyclic group having a ring (a carbonate ring) containing —O—C(═O)—O— in the ring skeleton thereof. In a case where the carbonate ring is counted as the first ring and the group contains only the carbonate ring, the group is referred to as a monocyclic group. Further, in a case where the group has other ring structures, the group is referred to as a polycyclic group regardless of the structures. The carbonate-containing cyclic group may be a monocyclic group or a polycyclic group.

The carbonate ring-containing cyclic group is not particularly limited, and any carbonate ring-containing cyclic group may be used. Specific examples thereof include groups each represented by General Formulae (ax3-r-1) to (ax3-r-3) shown below.

[In the formulae, each Ra′^(x31) independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or a cyano group; R″ represents a hydrogen atom, an alkyl group, a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂—-containing cyclic group; A″ represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 5 carbon atoms, which may contain an oxygen atom or a sulfur atom; and p′ represents an integer in a range of 0 to 3, and q′ is 0 or 1.]

In General Formulae (ax3-r-2) and (ax3-r-3), A″ has the same definition as that for A″ in General Formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, the alkoxy group, the halogen atom, the halogenated alkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl group, as Ra′³¹ include the same groups as those described in the explanation Ra′²¹ in General Formulae (a2-r-1) to (a2-r-7).

Specific examples of the groups each represented by General Formulae (ax3-r-1) to (ax3-r-3) are shown below.

Among them, the constitutional unit (a2) is preferably a constitutional unit derived from acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent.

The constitutional unit (a2) is preferably a constitutional unit represented by General Formula (a2-1).

[In the formula, R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Ya²¹ represents a single bond or a divalent linking group. La²¹ represents —O—, —COO—, —CON(R′)—, —OCO—, —CONHCO— or —CONHCS—, and R′ represents a hydrogen atom or a methyl group. However, in a case where La²¹ represents —O—, Ya²¹ does not represent —CO—. Ra²¹ represents a lactone-containing cyclic group, a carbonate-containing cyclic group, or a —SO₂—-containing cyclic group.]

In General Formula (a2-1), R has the same definition as described above. R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and particularly preferably a hydrogen atom or a methyl group in terms of industrial availability.

In General Formulae (a2-1), the divalent linking group as Ya²¹ is not particularly limited; however, suitable examples thereof include a divalent hydrocarbon group which may have a substituent and a divalent linking group containing a hetero atom, where the divalent hydrocarbon group is the same as the divalent hydrocarbon group exemplified in the explanation of W⁰¹ in General Formulae (a01-1).

Among the above, Ya²¹ is preferably a single bond, an ester bond [—C(═O)—O—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof.

In General Formula (a2-1), Ra²¹ represents a lactone-containing cyclic group, a —SO₂—-containing cyclic group, or a carbonate-containing cyclic group.

Suitable examples of the lactone-containing cyclic group, the —SO₂—-containing cyclic group, and the carbonate-containing cyclic group as Ra²¹ include groups each represented by General Formulae (a2-r-1) to (a2-r-7), groups each represented by General Formulae (a5-r-1) to (a5-r-4), and groups each represented by General Formulae (ax3-r-1) to (ax3-r-3) described above.

Among them, a lactone-containing cyclic group is preferable, and groups each represented by General Formulae (a2-r-1), (a2-r-2), or (a2-r-6), are more preferable. Specifically, groups each represented by any one of Chemical Formulae (r-1c-1-1) to (r-1c-1-7), (r-1c-2-1) to (r-1c-2-18), and (r-1c-6-1) are more preferable.

The constitutional unit (a2) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a2), the proportion of the constitutional unit (a2) is preferably in a range of 5% to 50% by mole and more preferably in a range of 10% to 45% by mole, with respect to the total (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a2) is set within the preferred range described above, the solubility of the developing solution can be appropriately ensured, and thus the effects according to the present invention can be more easily obtained.

In regard to constitutional unit (a3):

The component (A1) may further have the constitutional unit (a3) containing a polar group-containing aliphatic hydrocarbon group. In a case where the component (A1) has the constitutional unit (a3), the hydrophilicity of the component (A) is increased, which contributes to an improvement in resolution. Further, acid diffusion length can be appropriately adjusted.

Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, or a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group have been substituted with a fluorine atom, and the polar group is particularly preferably a hydroxyl group.

Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group (preferably an alkylene group) having 1 to 10 carbon atoms, and a cyclic aliphatic hydrocarbon group (a cyclic group). The cyclic group may be a monocyclic group or a polycyclic group. For example, these cyclic groups can be suitably selected from a large number of groups that have been proposed in resins for a resist composition for an ArF excimer laser.

In a case where the cyclic group is a monocyclic group, the monocyclic group preferably has 3 to 10 carbon atoms. Among them, a constitutional unit derived from an acrylic acid ester that includes an aliphatic monocyclic group containing a hydroxyl group, cyano group, carboxy group, or a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group have been substituted with a fluorine atom are particularly preferable. Examples of the monocyclic group include a group in which two or more hydrogen atoms have been removed from a monocycloalkane. Specific examples of the monocyclic group a include group in which two or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane, cyclohexane, or cyclooctane. Among these monocyclic groups, a group in which two or more hydrogen atoms have been removed from cyclopentane or a group in which two or more hydrogen atoms have been removed from cyclohexane are industrially preferable.

In a case where the cyclic group is a polycyclic group, the polycyclic group preferably has 7 to 30 carbon atoms. Among them, a constitutional unit derived from an acrylic acid ester that includes an aliphatic polycyclic group containing a hydroxyl group, cyano group, carboxy group, or a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group have been substituted with a fluorine atom is particularly preferable. Examples of the polycyclic group include groups in which two or more hydrogen atoms have been removed from a bicycloalkane, tricycloalkane, tetracycloalkane, or the like. Specific examples thereof include a group in which two or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Among these polycyclic groups, a group in which two or more hydrogen atoms have been removed from adamantane, a group in which two or more hydrogen atoms have been removed from norbornane, or a group in which two or more hydrogen atoms have been removed from tetracyclododecane are industrially preferable.

The constitutional unit (a3) is not particularly limited, and any constitutional unit may be used as long as the constitutional unit contains a polar group-containing aliphatic hydrocarbon group.

The constitutional unit (a3) is a constitutional unit derived from acrylic acid ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent, and a constitutional unit containing a polar group-containing aliphatic hydrocarbon group is preferable.

In a case where the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms, the constitutional unit (a3) is preferably a constitutional unit derived from a hydroxyethyl ester of acrylic acid.

Further, as the constitutional unit (a3), in a case where the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a polycyclic group, a constitutional unit represented by General Formula (a3-1), a constitutional unit represented by General Formula (a3-2), and a constitutional unit represented by General Formula (a3-3) are preferable, and in a case where the hydrocarbon group is a monocyclic group, a constitutional unit represented by General Formula (a3-4) is preferable.

[In the formulae, R has the same definition as described above, j represents an integer in a range of 1 to 3, k represents an integer in a range of 1 to 3, t′ represents an integer in a range of 1 to 3, 1 represents an integer in a range of 0 to 5, and s represents an integer in a range of 1 to 3.]

In General Formula (a3-1), j preferably represents 1 or 2 and more preferably 1. In a case where j represents 2, it is preferable that the hydroxyl groups be bonded to the 3- and 5-positions of the adamantyl group. In a case where j represents 1, it is preferable that the hydroxyl group be bonded to the 3-position of the adamantyl group.

It is preferable that j represent 1, and it is particularly preferable that the hydroxyl group be bonded to the 3-position of the adamantyl group.

In General Formula (a3-2), k preferably represents 1. The cyano group is preferably bonded to the 5- or 6-position of the norbornyl group.

In General Formula (a3-3), it is preferable that t′ represent 1. It is preferable that 1 represent 1. It is preferable that s represent 1. Further, it is preferable that a 2-norbornyl group or 3-norbornyl group be bonded to the terminal of the carboxy group of the acrylic acid. It is preferable that the fluorinated alkyl alcohol be bonded to the 5- or 6-position of the norbornyl group.

In General Formula (a3-4), it is preferable that t′ represent 1 or 2. It is preferable that 1 represent 0 or 1. It is preferable that s represent 1. It is preferable that the fluorinated alkyl alcohol be bonded to the 3- or 5-position of the cyclohexyl group.

The constitutional unit (a3) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a3), the proportion of the constitutional unit (a3) is preferably in a range of 1% to 30% by mole, more preferably in a range of 2% to 25% by mole, and still more preferably in a range of 5% to 25% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a3) is equal to or greater than the lower limit value of the preferred range, the effect obtained by allowing the component (A1) to contain the constitutional unit (a3) can be sufficiently achieved by the effect described above. In a case where the proportion of the constitutional unit (a3) is equal to or lower than the upper limit value of the preferred range, balance with other constitutional units can be obtained, and various lithography characteristics are improved.

In regard to constitutional unit (a10):

The constitutional unit (a10) is a constitutional unit represented by General Formula (a10-1).

[In the formula, R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Ya^(x1) represents a single bond or a divalent linking group. Wa^(x1) represents an aromatic hydrocarbon group which may have a substituent. n_(ax1) represents an integer of 1 or more.]

In General Formula (a10-1), R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms.

As the alkyl group having 1 to 5 carbon atoms as R, a linear or branched alkyl group having 1 to 5 carbon atoms is preferable, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

The halogenated alkyl group having 1 to 5 carbon atoms as R is a group in which part or all of hydrogen atoms of the above-described alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and in terms of industrial availability, R is more preferably a hydrogen atom, a methyl group, or trifluoromethyl group, still more preferably a hydrogen atom or a methyl group, and particularly preferably a methyl group.

In General Formula (a10-1), Ya^(x1) represents a single bond or a divalent linking group.

In the above chemical formula, the divalent linking group as Ya^(x1) is not particularly limited; however, suitable examples thereof include a divalent hydrocarbon group which may have a substituent and a divalent linking group containing a hetero atom, where the divalent hydrocarbon group is the same as the divalent hydrocarbon group exemplified in the explanation of W⁰¹ in General Formulae (a01-1).

Among the above, Ya^(x1) is preferably a single bond, an ester bond [—C(═O)—O—, —O—C(═O)—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof, and more preferably a single bond or an ester bond [—C(═O)—O—, —O—C(═O)—].

In General Formula (a10-1), Wa^(x1) represents an aromatic hydrocarbon group which may have a substituent.

Examples of the aromatic hydrocarbon group as Wa^(x1) include a group in which (n_(ax1)+1) hydrogen atoms have been removed from an aromatic ring which may have a substituent. The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons, and may be monocyclic or polycyclic. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and an aromatic heterocyclic ring in which a part of carbon atoms constituting the above-described aromatic hydrocarbon rings have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocyclic ring include a pyridine ring and a thiophene ring.

Examples of the aromatic hydrocarbon group as Wa^(x1) also include a group in which (n_(ax1)+1) hydrogen atoms have been removed from an aromatic compound including an aromatic ring (for example, biphenyl or fluorene) which may have two or more substituents.

Among the above, Wa^(x1) is preferably a group in which (n_(ax1)+1) hydrogen atoms have been removed from benzene, naphthalene, anthracene, or biphenyl, more preferably a group in which (n_(ax1)+1) hydrogen atoms have been removed from benzene or naphthalene, and still more preferably a group in which (n_(ax1)+1) hydrogen atoms have been removed from benzene.

The aromatic hydrocarbon group as Wa^(x1) may or may not have a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, and a halogenated alkyl group. Examples of the alkyl group, the alkoxy group, the halogen atom, and the halogenated alkyl group, as the substituent, include the same groups as those described as the above-described substituent of the cyclic aliphatic hydrocarbon group as Ya^(x1). The substituent is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, more preferably a linear or branched alkyl group having 1 to 3 carbon atoms, still more preferably an ethyl group or a methyl group, and particularly preferably a methyl group. The aromatic hydrocarbon group as Wa^(x1) preferably has no substituent.

In General Formula (a10-1), n_(ax1) represents an integer of 1 or greater, preferably an integer in a range of 1 to 10, more preferably an integer in a range of 1 to 5, still more preferably 1, 2, or 3, and particularly preferably 1 or 2.

Specific examples of the constitutional unit (a10) represented by General Formula (a10-1) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

The constitutional unit (a10) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a10), the proportion of the constitutional unit (a10) in the component (A1) is preferably in a range of 5% to 80% by mole, more preferably in a range of 10% to 75% by mole, still more preferably in a range of 30% to 70% by mole, and particularly preferably in a range of 40% to 60% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a10) is equal to or more than the lower limit value, the sensitivity can be more easily increased. On the other hand, in a case where the proportion of the constitutional unit (a10) is equal to or lower than the upper limit value, balance with other constitutional units is obtained easily.

In regard to constitutional unit (a8):

The constitutional unit (a8) is a constitutional unit derived from a compound represented by General Formula (a8-1).

[In the formula, W² represents a polymerizable group-containing group. Ya^(x2) represents a single bond or an (n_(ax2)+1)-valent linking group. Ya^(x2) and W² may form a condensed ring. R¹ represents a fluorinated alkyl group having 1 to 12 carbon atoms. R² represents an organic group having 1 to 12 carbon atoms, which may have a fluorine atom, or a hydrogen atom. n_(ax2) represents an integer in a range of 1 to 3.]

In General Formula (a8-1), the polymerizable group-containing group as W² is the same as the polymerizable group-containing group as W⁰¹ in General Formula (a01-1).

In General Formula (a8-1), Ya^(x2) represents a single bond or an (n_(ax2)+1)-valent, that is, a divalent, trivalent, or tetravalent linking group.

Examples of the divalent linking group as Ya^(x2) include the same group as that described as the divalent linking group as Ya^(x0) of W⁰¹ in General Formula (a01-1). Examples of the trivalent linking group as Ya^(x2) include a group in which one hydrogen atom has been removed from the above-described divalent linking group and a group in which the divalent linking group has been bonded to another divalent linking group. Examples of the tetravalent linking group include a group in which two hydrogen atoms are removed from the divalent linking group.

Ya^(x2) and W² may form a condensed ring.

In a case where Ya^(x2) and W² form a condensed ring, examples of the ring structure of the condensed ring include a condensed ring of an alicyclic hydrocarbon and an aromatic hydrocarbon. The condensed ring formed by Ya^(x2) and W² may have a hetero atom.

The alicyclic hydrocarbon moiety in the condensed ring formed by Ya^(x2) and W² may be a monocyclic ring or a polycyclic ring.

Examples of the condensed ring formed by Ya^(x2) and W² include a condensed ring formed by a polymerizable group of the W² moiety and by Ya^(x2) and a condensed ring formed by a group other than the polymerizable group of the W² moiety and by Ya^(x2). Specific examples thereof include a bicyclic condensed ring of a cycloalkene and an aromatic ring, a tricyclic condensed ring of a cycloalkene and two aromatic rings, and a bicyclic condensed ring of a cycloalkane having a polymerizable group as a substituent and an aromatic ring, and a tricyclic condensed ring of a cycloalkane having a polymerizable group as a substituent and an aromatic ring.

The condensed ring formed by Ya^(x2) and W² may have a substituent. Examples of this substituent include a methyl group, an ethyl group, propyl group, a hydroxy group, a hydroxyalkyl group, a carboxy group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, and the like), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and the like), an acyl group, an alkyloxycarbonyl group, and an alkyloxycarbonyloxy group.

Specific examples of the condensed ring formed by Ya^(x2) and W² are shown below. W^(α) represents a polymerizable group.

In General Formula (a8-1), R¹ represents a fluorinated alkyl group having 1 to 12 carbon atoms.

The fluorinated alkyl group having 1 to 12 carbon atoms is a group in which part or all of hydrogen atoms in the alkyl group having 1 to 12 carbon atoms have been substituted with a fluorine atom. The alkyl group may be linear or branched.

Specific examples of the linear fluorinated alkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and an undecyl group, a group in which part or all of hydrogen atom of a dodecyl group are substituted with a fluorine atom. Specific examples of the branched fluorinated alkyl group having 1 to 12 carbon atoms include a 1-methylethyl group, a 1,1-dimethylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a group in which part or all of hydrogen atoms of a 4-methylpentyl group are substituted with a fluorine atom.

Among the above, the fluorinated alkyl group having 1 to 12 carbon atoms of R¹ is preferably a fluorinated alkyl group having 1 to 5 carbon atoms and specifically preferably a trifluoromethyl group.

In General Formula (a8-1), R² represents an organic group having 1 to 12 carbon atoms, which may have a fluorine atom, or a hydrogen atom.

Examples of the organic group having 1 to 12 carbon atoms as R², which may have a fluorine atom, include a monovalent hydrocarbon group having 1 to 12 carbon atoms, which may have a fluorine atom.

Examples of the hydrocarbon group include a linear or branched alkyl group and a cyclic hydrocarbon group.

Specific examples of the linear alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.

Specific examples of the branched alkyl group include a 1-methylethyl group, a 1,1-dimethylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

In a case where R² represents a cyclic hydrocarbon group, the cyclic hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group and may be a polycyclic group or a monocyclic group.

The aliphatic hydrocarbon group which is a monocyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.

The aliphatic hydrocarbon group which is a polycyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane. The polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

In a case where the cyclic hydrocarbon group as R² is an aromatic hydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring. Specific examples of the aromatic hydrocarbon group include a group in which one hydrogen atom has been removed from an aromatic hydrocarbon ring such as benzene, naphthalene, anthracene, phenanthrene, biphenyl, and fluorene.

The organic group having 1 to 12 carbon atoms as R² may have a substituent other than a fluorine atom. Examples of the substituent include a hydroxy group, a carboxy group, a halogen atom (a chlorine atom, a bromine atom, and the like), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and the like), and an alkyloxycarbonyl group.

R² is preferably a fluorinated alkyl group having 1 to 12 carbon atoms, more preferably a fluorinated alkyl group having 1 to 5 carbon atoms, and still more preferably a trifluoromethyl group.

In General Formula (a8-1), n_(ax2) represents an integer in a range of 1 to 3, preferably 1 or 2, and more preferably 1.

The constitutional unit (a8) is preferably a constitutional unit (a81) derived from a compound represented by General Formula (a8-1-1).

[In General Formula (a8-1-1), W² represents a polymerizable group-containing group. Wa^(x2) represents an (n_(ax2)+1) valent cyclic group. W² and Wa^(x2) may form a condensed ring. R¹ represents a fluorinated alkyl group having 1 to 12 carbon atoms. R² represents an organic group having 1 to 12 carbon atoms, which may have a fluorine atom, or a hydrogen atom. n_(ax2) represents an integer in a range of 1 to 3.]

In General Formula (a8-1-1), W², R¹, R², and n_(ax2) are each the same as W², R¹, R², and n_(ax2) in General Formula (a8-1).

In General Formula (a8-1-1), Wa^(x2) is a (n_(ax2)+1) valent cyclic group.

Examples of the cyclic group as Wa^(x2) include an aliphatic cyclic group and an aromatic cyclic group, and the cyclic group may be a monocyclic ring or a polycyclic ring.

The aliphatic cyclic group which is a monocyclic group is preferably a group in which one hydrogen atom has been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane.

The aliphatic cyclic group which is a polycyclic group is preferably a group in which one hydrogen atom has been removed from a polycycloalkane. The polycycloalkane preferably has 7 to 12 carbon atoms, and specific examples thereof include a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as decalin, perhydroazulene, or perhydroanthracene.

The aromatic cyclic group is a hydrocarbon group having at least one aromatic ring. The aromatic ring is not particularly limited as long as it is a cyclic conjugated system having (4n+2) π electrons. The aromatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbon atoms, and particularly preferably 6 to 12 carbon atoms. Specific examples of the aromatic ring include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; and an aromatic heterocyclic ring in which a part of carbon atoms constituting the above-described aromatic hydrocarbon ring have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom. Specific examples of the aromatic heterocyclic ring include a pyridine ring and a thiophene ring. Specific examples of the aromatic hydrocarbon group include a group in which one hydrogen atom has been removed from the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring (an aryl group or a heteroaryl group); a group in which one hydrogen atom has been removed from an aromatic compound having two or more aromatic rings (biphenyl, fluorene or the like); and a group in which one hydrogen atom of the above-described aromatic hydrocarbon ring or aromatic heterocyclic ring has been substituted with an alkylene group (an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group bonded to the aromatic hydrocarbon ring or aromatic heterocyclic ring preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

Examples of the substituent which the cyclic group as Wa^(x2) may have include a carboxy group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, and the like), an alkoxy group (a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and the like), and an alkyloxycarbonyl group.

W² and Wa^(x2) may form a condensed ring, which is the same condensed ring as that described in the condensed ring formed by Ya^(x2) and W² in General Formula (a8-1).

Specific examples of the constitutional unit (a8) are as follows.

In the formulae shown below, R^(α) represents a hydrogen atom, a methyl group, or a trifluoromethyl group.

Among the above examples, the constitutional unit (a8) is preferably a constitutional unit represented by Chemical Formula (a8-1-01).

The constitutional unit (a8) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a8), the proportion of the constitutional unit (a8) is preferably in a range of 1% to 50% by mole, more preferably in a range of 1% to 30% by mole, and still more preferably in a range of 5% to 20% by mole, with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a8) is equal to or greater than the lower limit value of the preferred range, the compatibility with the developing solution and the rinse liquid can be enhanced. On the other hand, in a case where the proportion is equal to or lower than the upper limit value of the preferred range, balance with other constitutional units can be obtained, and various lithography characteristics are improved.

In regard to constitutional unit (a4):

The component (A1) may further have a constitutional unit (a4) containing an acid non-dissociable aliphatic cyclic group.

In a case where the component (A1) has the constitutional unit (a4), the dry etching resistance of the formed resist pattern is improved. Further, the hydrophobicity of the component (A) increases. The improvement in hydrophobicity contributes to the improvement in resolution, a resist pattern shape, and the like, particularly in the case of a solvent developing process.

The “acid non-dissociable cyclic group” in the constitutional unit (a4) is a cyclic group that remains in the constitutional unit without being dissociated even when an acid acts in a case where the acid is generated in the resist composition by exposure (for example, in a case where an acid is generated from the constitutional unit or the component (B), which generates an acid upon exposure).

Examples of the constitutional unit (a4) preferably include a constitutional unit derived from an acrylic acid ester including an acid non-dissociable aliphatic cyclic group. As the cyclic group, many cyclic groups conventionally known as cyclic groups used as a resin component of a resist composition for ArF excimer laser, KrF excimer laser (preferably ArF excimer laser), or the like can be used.

The cyclic group is particularly preferably at least one selected from a tricyclodecyl group, an adamantyl group, a tetracyclododecyl group, an isobornyl group, and a norbomyl group, from the viewpoint of industrial availability. These polycyclic groups may have, as a substituent, a linear or branched alkyl group having 1 to 5 carbon atoms.

Specific examples of the constitutional unit (a4) include constitutional units each represented by General Formulae (a4-1) to (a4-7).

[In the formula, R^(α) is the same as above.]

The constitutional unit (a4) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (a4), the proportion of the constitutional unit (a4) is preferably in a range of 1% to 40% by mole and more preferably in a range of 5% to 20% by mole, with respect to the total (100% by mole) of all constitutional units constituting the component (A1).

In a case where the proportion of the constitutional unit (a4) is equal to or greater than the lower limit value of the preferred range, the effect that is obtained by allowing the component (A1) to contain the constitutional unit (a4) can be sufficiently achieved. In a case where the proportion of the constitutional unit (a4) is equal to or lower than the upper limit value of the preferred range, the balance with other constitutional units is obtained easily.

In regard to constitutional unit (st):

The constitutional unit (st) is a constitutional unit derived from styrene or a styrene derivative. A “constitutional unit derived from styrene” means a constitutional unit that is formed by the cleavage of an ethylenic double bond of styrene. A “constitutional unit derived from a styrene derivative” means a constitutional unit (provided that a constitutional unit corresponding to the constitutional unit (a10) is excluded) formed by the cleavage of an ethylenic double bond of a styrene derivative.

The “styrene derivative” means a compound in which at least a part of hydrogen atoms of styrene are substituted with a substituent. Examples of the styrene derivative include a derivative in which the hydrogen atom at the α-position of styrene is substituted with a substituent, a derivative in which one or more hydrogen atoms of the benzene ring of styrene are substituted with a substituent, and a derivative in which the hydrogen atom at the α-position of styrene and one or more hydrogen atoms of the benzene ring are substituted with a substituent.

Examples of the substituent that is substituted for the hydrogen atom at the α-position of styrene include an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms.

The alkyl group having 1 to 5 carbon atoms is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

The halogenated alkyl group having 1 to 5 carbon atoms is a group in which part or all of hydrogen atoms in the alkyl group having 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is particularly preferably a fluorine atom.

The substituent that is substituted for the hydrogen atom at the α-position of styrene is preferably an alkyl group having 1 to 5 carbon atoms or a fluorinated alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms or a fluorinated alkyl group having 1 to 3 carbon atoms, and still more preferably a methyl group from the viewpoint of industrial availability.

Examples of the substituent that is substituted for the hydrogen atom of the benzene ring of styrene include an alkyl group, an alkoxy group, a halogen atom, and a halogenated alkyl group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and still more preferably a methoxy group or an ethoxy group.

The halogen atom as the substituent is preferably a fluorine atom.

Examples of the halogenated alkyl group as the substituent include groups in which part or all of hydrogen atoms in the above-described alkyl groups have been substituted with the above-described halogen atoms.

The substituent that is substituted for the hydrogen atom of the benzene ring of styrene is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group or an ethyl group, and still more preferably a methyl group.

The constitutional unit (st) is preferably a constitutional unit derived from styrene or a constitutional unit derived from a styrene derivative in which the hydrogen atom at the α-position of styrene is substituted with an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms, more preferably a constitutional unit derived from styrene, or a constitutional unit derived from a styrene derivative in which the hydrogen atom at the α-position of styrene is substituted with a methyl group, and still more preferably a constitutional unit derived from styrene.

The constitutional unit (st) which the component (A1) has may be one kind or may be two or more kinds.

In a case where the component (A1) has the constitutional unit (st), the proportion of the constitutional unit (st) is preferably in a range of 1% to 30% by mole and more preferably in a range of 3% to 20% by mole with respect to the total amount (100% by mole) of all constitutional units constituting the component (A1).

The component (A1) contained in the resist composition may be used alone or in a combination of two or more kinds thereof.

In the resist composition according to the present embodiment, the component (A1) is a resin component that contains the constitutional unit (a01).

Examples of the component (A1) include a polymer compound having a repeated structure of the constitutional unit (a01).

Preferred examples of the component (A1) include a polymer compound having a repeated structure of the constitutional unit (a01) and the constitutional unit (a10); a polymer compound having a repeated structure of the constitutional unit (a01), the constitutional unit (a10), and the constitutional unit (a8); a polymer compound having a repeated structure of the constitutional unit (a01) and the constitutional unit (a2); and a polymer compound having a repeated structure of the constitutional unit (a01), the constitutional unit (a2), and the constitutional unit (a3). Among them, from the viewpoint of further improving the sensitivity and the exposure margin, a polymer compound having a repeated structure of the constitutional unit (a01) and the constitutional unit (a10) is preferable, and a polymer compound having a repeated structure of the constitutional unit (a01) and the constitutional unit (a10) or a polymer compound having a repeated structure of the constitutional unit (a01), the constitutional unit (a10), and the constitutional unit (a8) is more preferable. From the viewpoint of improving the sensitivity, a polymer compound having a repeated structure of the constitutional unit (a01) and the constitutional unit (a10) is preferable, and from the viewpoint of improving the exposure margin, a polymer compound having a repeated structure of the constitutional unit (a01), the constitutional unit (a10), and the constitutional unit (a8) is preferable.

In the polymer compound having a repeated structure of the constitutional unit (a01) and the constitutional unit (a10), the proportion of the constitutional unit (a01) in the polymer compounds is preferably in a range of 20% to 80% by mole, more preferably in a range of 30% to 70% by mole, and still more preferably in a range of 35% to 65% by mole, with respect to the total (100% by mole) of all constitutional units constituting the polymer compound.

In addition, the proportion of the constitutional unit (a10) in the polymer compound is preferably in a range of 20% to 80% by mole, more preferably in a range of 30% to 70% by mole, still more preferably in a range of 35% to 65% by mole, with respect to the total (100% by mole) of all constitutional units constituting the polymer compound.

In the polymer compound having a repeated structure of the constitutional unit (a01), the constitutional unit (a10), and the constitutional unit (a8), the proportion of the constitutional unit (a01) in the polymer compounds is preferably in a range of 20% to 80% by mole, more preferably in a range of 30% to 70% by mole, and still more preferably in a range of 40% to 55% by mole, with respect to the total (100% by mole) of all constitutional units constituting the polymer compound.

In addition, the proportion of the constitutional unit (a10) in the polymer compound is preferably in a range of 20% to 80% by mole, more preferably in a range of 30% to 70% by mole, still more preferably in a range of 30% to 55% by mole, with respect to the total (100% by mole) of all constitutional units constituting the polymer compound.

In addition, the proportion of the constitutional unit (a8) in the polymer compound is preferably in a range of 1% to 50% by mole, more preferably in a range of 1% to 30% by mole, still more preferably in a range of 5% to 15% by mole, with respect to the total (100% by mole) of all constitutional units constituting the polymer compound.

The component (A1) can be produced by dissolving, in a polymerization solvent, each monomer from which the constitutional unit is derived, adding thereto a radical polymerization initiator such as azobisisobutyronitrile (AIBN) or dimethyl azobisisobutyrate (for example, V-601) to perform polymerization.

Alternatively, the component (A1) can be produced by dissolving, in a polymerization solvent, a monomer from which the constitutional unit (a01) is derived and, as necessary, a monomer (for example, a compound in which a hydroxyl group of a monomer from which the constitutional unit (a10) is derived is protected) from which a constitutional unit other than the constitutional unit (a1) is derived, and adding thereto a radical polymerization initiator as described above to perform polymerization and then performing a deprotection reaction.

Further, a —C(CF₃)₂—OH group may be introduced into the terminal of the component (A1) during the polymerization using a chain transfer agent such as HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH in combination. As described above, a copolymer into which a hydroxyalkyl group, formed by substitution of a part of hydrogen atoms in the alkyl group with fluorine atoms, has been introduced is effective for reducing development defects and reducing line edge roughness (LER: uneven irregularities of a line side wall).

The weight-average molecular weight (Mw) (based on the polystyrene-equivalent value determined by gel permeation chromatography (GPC)) of the component (A1), which is not particularly limited, is preferably in a range of 1,000 to 50,000, more preferably in a range of 2,000 to 30,000, and still more preferably in a range of 3,000 to 20,000.

In a case where Mw of the component (A1) is equal to or lower than the upper limit value of this preferred range, the resist composition exhibits sufficient solubility in a solvent for a resist such that the resist composition can be used as a resist. On the other hand, in a case where Mw of the component (A1) is equal to or greater than the lower limit value of this preferred range, dry etching resistance and the cross-sectional shape of the resist pattern become excellent.

Further, the dispersity (Mw/Mn) of the component (A1) is not particularly limited; however, it is preferably in a range of 1.0 to 4.0, more preferably in a range of 1.0 to 3.0, and particularly preferably in a range of 1.0 to 2.0. Mn represents the number-average molecular weight.

In regard to component (A2)

In the resist composition according to the present embodiment, a base material component (hereinafter, referred to as a “component (A2)”) exhibiting changed solubility in a developing solution under action of acid, which does not correspond to the component (A1), may be used in combination as the component (A).

The component (A2) is not particularly limited and may be freely selected and used from a large number of conventionally known base material components for the chemical amplification-type resist composition.

As the component (A2), a polymer compound or a low-molecular-weight compound may be used alone or in a combination of two or more kinds thereof.

The proportion of the component (A1) in the component (A) is preferably 25% by mass or greater, more preferably 50% by mass or greater, still more preferably 75% by mass or greater, and may be 100% by mass with respect to the total mass of the component (A). In a case where the proportion is 25% by mass or more, a resist pattern having various excellent lithography characteristics such as high sensitivity, resolution, and roughness amelioration can be easily formed.

The content of the component (A) in the resist composition according to the present embodiment may be adjusted depending on the resist film thickness to be formed and the like.

<Other Components>

The resist composition according to the present embodiment may further contain other components in addition to the component (A) described above. Examples of the other components include a component (B), a component (D), a component (E), a component (F), and a component (S), which are described below.

<<Acid Generator Component (B)>>

The resist composition according to the present embodiment may further contain an acid generator component (B) (hereinafter, referred to as a “component (B)”) generating an acid upon exposure, in addition to the component (A).

The component (B) is not particularly limited, and those which have been proposed so far as an acid generator for a chemical amplification-type resist composition can be used.

Examples of these acid generators are numerous and include onium salt-based acid generators such as iodonium salts and sulfonium salts; oxime sulfonate-based acid generators; diazomethane-based acid generators such as bisalkyl or bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes; nitrobenzyl sulfonate-based acid generators; iminosulfonate-based acid generators; and disulfonate-based acid generators.

Examples of the onium salt-based acid generator include a compound represented by General Formula (b-1) (hereinafter, also referred to as a “component (b-1)”), a compound represented by General Formula (b-2) (hereinafter, also referred to as a “component (b-2)”), and a compound represented by General Formula (b-3) (hereinafter, also referred to as a “component (b-3)”).

In the formulae, R¹⁰ and R¹⁰⁴ to R¹⁰⁸ each independently represent a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent. R¹⁰⁴ and R¹⁰⁵ may be bonded to each other to form a ring structure. R¹⁰² represents a fluorinated alkyl group having 1 to 5 carbon atoms or a fluorine atom. Y¹⁰¹ represents a divalent linking group containing an oxygen atom or a single bond. V¹⁰¹ to V¹⁰³ each independently represents a single bond, an alkylene group, or a fluorinated alkylene group. L¹⁰¹ and L¹⁰² each independently represent a single bond or an oxygen atom. L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO—, or —SO₂—. m represents an integer of 1 or greater, and M′^(m+) represents an m-valent onium cation.]

{Anion Moiety}

Anion in Component (b-1)

In General Formula (b-1), R¹⁰¹ represents a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent.

Cyclic group which may have substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group. The aliphatic hydrocarbon group indicates a hydrocarbon group that has no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated.

The aromatic hydrocarbon group as R¹⁰¹ is a hydrocarbon group having an aromatic ring. The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30, still more preferably 5 to 20, particularly preferably 6 to 15, and most preferably 6 to 10. Here, the number of carbon atoms in a substituent is not included in the number of carbon atoms.

Specific examples of the aromatic ring the aromatic hydrocarbon group has as R¹⁰¹ include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or an aromatic heterocyclic ring in which some carbon atoms constituting any of these aromatic rings have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group as R¹⁰¹ include a group in which one hydrogen atom has been removed from the above-described aromatic ring (an aryl group; for example, a phenyl group or a naphthyl group) and a group in which one hydrogen atom in the aromatic ring has been substituted with an alkylene group (an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group (an alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

Examples of the cyclic aliphatic hydrocarbon group as R¹⁰¹ include aliphatic hydrocarbon groups containing a ring in the structure thereof.

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include an alicyclic hydrocarbon group (a group in which one hydrogen atom has been removed from an aliphatic hydrocarbon ring), a group in which the alicyclic hydrocarbon group is bonded to the terminal of a linear or branched aliphatic hydrocarbon group, and a group in which the alicyclic hydrocarbon group is interposed in a linear or branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms and more preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 30 carbon atoms. Among the above, the polycycloalkane is more preferably a polycycloalkane having a bridged ring-based polycyclic skeleton, such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; or a polycycloalkane having a condensed ring-based polycyclic skeleton, such as a cyclic group having a steroid skeleton.

Among them, the cyclic aliphatic hydrocarbon group as R¹⁰¹ is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane, more preferably a group in which one hydrogen atom has been removed from a polycycloalkane, particularly preferably an adamantyl group or a norbornyl group, and most preferably an adamantyl group.

The linear aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms. The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4 carbon atoms, and most preferably 3 carbon atoms. The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylalkylene groups, for example, alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The cyclic hydrocarbon group as R¹⁰¹ may contain a hetero atom such as a heterocyclic ring. Specific examples thereof include lactone-containing cyclic groups each represented by General Formulae (a2-r-1) to (a2-r-7), —SO₂—-containing cyclic groups each represented by General Formulae (a5-r-1) to (a5-r-4), and other heterocyclic groups each represented by Chemical Formulae (r-hr-1) to (r-hr-16). In the formulae, * represents a bonding site that is bonded to Y¹⁰¹ in General Formula (b-1).

Examples of the substituent of the cyclic group as R¹⁰¹ include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, and a nitro group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.

Examples of the above-described halogenated alkyl group as the substituent include a group in which part or all of hydrogen atoms in an alkyl group having 1 to 5 carbon atoms such as a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group have been substituted with the above-described halogen atom.

The carbonyl group as the substituent is a group that substitutes a methylene group (—CH₂—) constituting the cyclic hydrocarbon group.

The cyclic hydrocarbon group as R¹⁰¹ may be a condensed ring-type group containing a condensed ring in which an aliphatic hydrocarbon ring and an aromatic ring are condensed. Examples of the condensed ring include a condensed ring in which one or more aromatic rings are condensed with a polycycloalkane having a bridged ring-based polycyclic skeleton. Specific examples of the bridged ring-based polycycloalkane include bicycloalkanes such as bicyclo [2.2.1]heptane (norbornane) and bicyclo[2.2.2]octane. The condensed ring type is preferably a group containing a condensed ring, in which two or three aromatic rings are condensed with a bicycloalkane, and more preferably a group containing a condensed ring, in which two or three aromatic rings are condensed with bicyclo[2.2.2]octane. Specific examples of the condensed ring-type group as R¹⁰¹ include those represented by General Formulae (r-br-1) to (r-br-2). In the formulae, * represents a bonding site that is bonded to Y¹⁰¹ in General Formula (b-1).

Examples of the substituent which the condensed ring-type group as R¹⁰¹ may have include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, a nitro group, an aromatic hydrocarbon group, and an alicyclic hydrocarbon group.

Examples of the alkyl group, the alkoxy group, the halogen atom, and the halogenated alkyl group, as the substituent of the condensed ring-type group, include the same groups as those described as the substituent of the cyclic group as R¹⁰¹.

Examples of the aromatic hydrocarbon group as the substituent of the condensed ring-type group include a group in which one hydrogen atom has been removed from the above-described aromatic ring (an aryl group; for example, a phenyl group or a naphthyl group), a group in which one hydrogen atom in the aromatic ring has been substituted with an alkylene group (for example, an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, 1-naphthylethyl group, or a 2-naphthylethyl group), and heterocyclic groups each represented by General Formulae (r-hr-1) to (r-hr-6).

Examples of the alicyclic hydrocarbon group as the substituent of the condensed ring-type group include a group in which one hydrogen atom has been removed from a monocycloalkane such as cyclopentane or cyclohexane; a group in which one hydrogen atom has been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; lactone-containing cyclic groups each represented by General Formulae (a2-r-1) to (a2-r-7); —SO₂—-containing cyclic groups each represented by General Formulae (a5-r-1) to (a5-r-4); and heterocyclic groups each represented by General Formulae (r-hr-7) to (r-hr-16).

Chain-like alkyl group which may have substituent:

The chain-like alkyl group as R¹⁰¹ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms.

The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to 10. Specific examples thereof include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

Chain-like alkenyl group which may have substituent:

A chain-like alkenyl group as R¹⁰¹ may be linear or branched, and the chain-like alkenyl group preferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, still more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. Examples of the linear alkenyl group include a vinyl group, a propenyl group (an allyl group), and a butynyl group. Examples of the branched alkenyl group include a 1-methylvinyl group, a 2-methylvinyl group, a 1-methylpropenyl group, and a 2-methylpropenyl group.

Among the above, the chain-like alkenyl group is preferably a linear alkenyl group, more preferably a vinyl group or a propenyl group, and particularly preferably a vinyl group.

Examples of the substituent in the chain-like alkyl group or alkenyl group as R¹⁰¹, include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, a nitro group, an amino group, and a cyclic group as R¹⁰¹.

Among the above, R¹⁰¹ is preferably a cyclic group which may have a substituent and more preferably a cyclic hydrocarbon group which may have a substituent. More specific examples of the cyclic hydrocarbon group preferably include a phenyl group, a naphthyl group, a group in which one or more hydrogen atoms have been removed from a polycycloalkane, lactone-containing cyclic groups each represented by any one of General Formulae (a2-r-1) to (a2-r-7), and —SO₂—-containing cyclic groups each represented by any one of General Formulae (a5-r-1) to (a5-r-4).

In General Formula (b-1), Y¹⁰¹ represents a single bond or a divalent linking group containing an oxygen atom.

In a case where Y¹⁰¹ represents a divalent linking group containing an oxygen atom, Y¹⁰¹ may contain an atom other than the oxygen atom. Examples of atom other than the oxygen atom include a carbon atom, a hydrogen atom, a sulfur atom, and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom include non-hydrocarbon-based oxygen atom-containing linking groups such as an oxygen atom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonyl group (—O—C(═O)—), an amide bond (—C(═O)—NH—), a carbonyl group (—C(═O)—), or a carbonate bond (—O—C(═O)—O—); and combinations of the above-described non-hydrocarbon-based oxygen atom-containing linking groups with an alkylene group. Furthermore, a sulfonyl group (—SO₂—) may be linked to the combination. Examples of divalent linking groups containing an oxygen atom include linking groups each represented by General Formulae (y-a1-1) to (y-a1-7) shown below.

[In the formulae, V′¹⁰¹ represents a single bond or an alkylene group having 1 to 5 carbon atoms, and V′¹⁰² represents a divalent saturated hydrocarbon group having 1 to 30 carbon atoms.]

The divalent saturated hydrocarbon group as V′¹⁰² is preferably an alkylene group having 1 to 30 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, and still more preferably an alkylene group having 1 to 5 carbon atoms.

The alkylene group as V′¹⁰¹ and V′¹⁰² may be a linear alkylene group or a branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group as V′¹⁰¹ and V′¹⁰² include a methylene group [—CH₂—]; an alkylmethylene group such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, or —C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, or —CH(CH₂CH₃)CH₂—; a trimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; an alkyltrimethylene group such as —CH(CH₃)CH₂CH₂— or —CH₂CH(CH₃)CH₂—; a tetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group such as —CH(CH₃)CH₂CH₂CH₂—, or —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

Further, a part of a methylene group in the alkylene group as V′¹⁰¹ and V′¹⁰² may be substituted with a divalent aliphatic cyclic group having 5 to 10 carbon atoms. The aliphatic cyclic group is preferably a divalent group in which one hydrogen atom has been removed from the cyclic aliphatic hydrocarbon group (a monocyclic aliphatic hydrocarbon group or a polycyclic aliphatic hydrocarbon group) as Ra′³ in General Formula (a1-r-1), and a cyclohexylene group, a 1,5-adamantylene group, or a 2,6-adamantylene group is more preferable.

Y¹⁰¹ preferably represents a divalent linking group containing an ester bond or a divalent linking group containing an ether bond and more preferably linking groups each represented by General Formulae (y-a1-1) to (y-a1-5).

In General Formula (b-1), V¹⁰¹ represents a single bond, an alkylene group, or a fluorinated alkylene group. The alkylene group and the fluorinated alkylene group as V¹⁰¹ preferably have 1 to 4 carbon atoms. Examples of the fluorinated alkylene group as V¹⁰¹ include a group in which part or all of hydrogen atoms in the alkylene group as V¹⁰¹ have been substituted with a fluorine atom. Among these examples, as V¹⁰¹, a single bond or a fluorinated alkylene group having 1 to 4 carbon atoms is preferable.

In General Formula (b-1), R¹⁰² represents a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. R¹⁰² preferably represents a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms and more preferably a fluorine atom.

As a specific example of the anion moiety represented by Formula (b-1), in a case where Y¹⁰¹ represents a single bond, a fluorinated alkyl sulfonate anion such as a trinfluoromethanesulfonate anion or a perfluorobutanesulfonate anion can be mentioned; and in a case where Y¹⁰¹ represents a divalent linking group containing an oxygen atom, anions represented by Formulae (an-1) to (an-3) shown below can be mentioned.

[In the formula, R″¹⁰¹ represents an aliphatic cyclic group which may have a substituent, monovalent heterocyclic groups each represented by Chemical Formulae (r-hr-1) to (r-hr-6), a condensed ring-type group represented by General Formula (r-br-1) or (r-br-2), and a chain-like alkyl group which may have a substituent. R″¹⁰² is an aliphatic cyclic group which may have a substituent, a condensed ring-type group represented by General Formula (r-br-1) or (r-br-2), lactone-containing cyclic groups each represented by General Formulae (a2-r-1), (a2-r-3) to (a2-r-7), or —SO₂—-containing cyclic groups each represented by General Formulae (a5-r-1) to (a5-r-4). R″¹⁰³ represents an aromatic cyclic group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain-like alkenyl group which may have a substituent. V″¹⁰¹ represents a single bond, an alkylene group having 1 to 4 carbon atoms, or a fluorinated alkylene group having 1 to 4 carbon atoms. R¹⁰² represents a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. Each v″ independently represents an integer in a range of 0 to 3, each q″ independently represent an integer in a range of 0 to 20, and n″ represents 0 or 1.]

The aliphatic cyclic group as R″¹⁰¹, R″¹⁰², and R″¹⁰³ which may have a substituent is preferably the group exemplified as the cyclic aliphatic hydrocarbon group as R¹⁰¹ in General Formula (b-1). Examples of the substituent include the same group as the substituent with which the cyclic aliphatic hydrocarbon group as R¹⁰¹ in General Formula (b-1) may be substituted.

The aromatic cyclic group which may have a substituent, as R″¹⁰³, is preferably the group exemplified as the aromatic hydrocarbon group for the cyclic hydrocarbon group as R¹⁰¹ in General Formula (b-1). Examples of the substituent include the same groups as the substituent with which the aromatic hydrocarbon group as R¹⁰¹ in General Formula (b-1) may be substituted.

The chain-like alkyl group as R″¹⁰¹, which may have a substituent, is preferably the group exemplified as the chain-like alkyl group as R¹⁰¹ in General Formula (b-1). The chain-like alkenyl group as R″¹⁰³, which may have a substituent, is preferably the group exemplified as the chain-like alkenyl group as R¹⁰¹ in General Formula (b-1).

Anion in Component (b-2)

In Formula (b-2), R¹⁰⁴ and R¹⁰⁵ each independently represent a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent, and are each the same as R¹⁰¹ in Formula (b-1). However, R¹⁰⁴ and R¹⁰⁵ may be bonded to each other to form a ring.

R¹⁰⁴ and R¹⁰⁵ are preferably a chain-like alkyl group which may have a substituent and more preferably a linear or branched alkyl group or a linear or branched fluorinated alkyl group.

The chain-like alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbon atoms. It is preferable that the number of carbon atoms in the chain-like alkyl group as R¹⁰⁴ and R¹⁰⁵ be small since the solubility in a solvent for a resist is also excellent in this range of the number of carbon atoms. Further, in the chain-like alkyl group as R¹⁰⁴ and R¹⁰⁵, it is preferable that the number of hydrogen atoms substituted with a fluorine atom be large since the acid strength increases and the transparency to high energy radiation of 250 nm or less or electron beams is improved. The proportion of fluorine atoms in the chain-like alkyl group, that is, the fluorination ratio is preferably in a range of 70% to 100% and more preferably in a range of 90% to 100%, and it is most preferable that the chain-like alkyl group be a perfluoroalkyl group in which all hydrogen atoms be substituted with a fluorine atom.

In General Formula (b-2), V¹⁰² and V¹⁰³ each independently represent a single bond, an alkylene group, or a fluorinated alkylene group, and examples thereof include those that are the same as V¹⁰¹ in General Formula (b-1).

in General Formula (b-2), L¹⁰¹ and L¹⁰² each independently represent a single bond or an oxygen atom.

Anion in Component (b-3)

In Formula (b-3), R¹⁰⁶ to R¹⁰⁸ each independently represents a cyclic group which may have a substituent, chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent, and examples thereof include the same group as R¹⁰¹ in Formula (b-1).

In General Formula (b-3), L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO—, or —SO₂—.

Among the above, the anion moiety of the component (B) is preferably an anion of the component (b-1). Among these, an anion represented by any one of General Formulae (an-1) to (an-3) is more preferable, an anion represented by any one of General Formula (an-1) or (an-2) is still more preferable, and an anion represented by General Formula (an-2) is particularly preferable.

{Cation Moiety}

In Formulae (b-1), (b-2), and (b-3), M′^(m)+ represents an m-valent onium cation. Among them, a sulfonium cation and an iodonium cation are preferable.

m represents an integer of 1 or greater.]

Preferred examples of the cation moiety ((M′^(m+))_(l/m)) include organic cations each represented by General Formulae (ca-1) to (ca-5).

[In the formula, R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² each independently represent an aryl group, an alkyl group, or an alkenyl group, each of which may have a substituent. R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹ and R²¹² may be bonded to each other to form a ring together with the sulfur atoms in the formulae. R²⁰⁸ and R²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R²¹⁰ represents an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a —SO₂—-containing cyclic group which may have a substituent. L²⁰¹ represents —C(═O)— or —C(═O)—O—. Each Y²⁰¹ independently represent an arylene group, an alkylene group, or an alkenylene group. x represents 1 or 2. W²⁰¹ represents an (x+1)-valent linking group.]

In General Formulae (ca-1) to (ca-5), examples of the aryl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² include an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group or a naphthyl group is preferable.

The alkyl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² is preferably a chain-like or cyclic alkyl group preferably has 1 to 30 carbon atoms.

The alkenyl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² preferably has 2 to 10 carbon atoms.

Examples of the substituent which may be included in R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² include an alkyl group, a halogen atom, a halogenated alkyl group, a carbonyl group, a cyano group, an amino group, an aryl group, and groups each represented by General Formulae (ca-r-1) to (ca-r-7) shown below.

[In the formulae, each R′²⁰¹ independently represent a hydrogen atom, a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent.]

Cyclic group which may have substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group. The aliphatic hydrocarbon group indicates a hydrocarbon group that has no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated. In general, it is preferable that the aliphatic hydrocarbon group be saturated.

The aromatic hydrocarbon group as R′²⁰¹ is a hydrocarbon group having an aromatic ring. The aromatic hydrocarbon group preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, particularly preferably 6 to 15 carbon atoms, and most preferably 6 to 10 carbon atoms. Here, the number of carbon atoms in a substituent is not included in the number of carbon atoms.

Specific examples of the aromatic ring which the aromatic hydrocarbon group has as R′²⁰¹ include benzene, fluorene, naphthalene, anthracene, phenanthrene, biphenyl, or an aromatic heterocyclic ring in which some carbon atoms constituting any of these aromatic rings have been substituted with a hetero atom. Examples of the hetero atom in the aromatic heterocyclic rings include an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group as R′²⁰¹ include a group in which one hydrogen atom has been removed from the above-described aromatic ring (an aryl group; for example, a phenyl group or a naphthyl group) and a group in which one hydrogen atom in the aromatic ring has been substituted with an alkylene group (for example, an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, 1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group (an alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

Examples of the cyclic aliphatic hydrocarbon group as R′²⁰¹ include aliphatic hydrocarbon groups containing a ring in the structure thereof.

Examples of the aliphatic hydrocarbon group containing a ring in the structure thereof include an alicyclic hydrocarbon group (a group in which one hydrogen atom has been removed from an aliphatic hydrocarbon ring), a group in which the alicyclic hydrocarbon group is bonded to the terminal of a linear or branched aliphatic hydrocarbon group, and a group in which the alicyclic hydrocarbon group is interposed in a linear or branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms and more preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. The monocyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane, and the polycycloalkane preferably has 7 to 30 carbon atoms. Among the above, the polycycloalkane is more preferably a polycycloalkane having a bridged ring-based polycyclic skeleton, such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane; or a polycycloalkane having a condensed ring-based polycyclic skeleton, such as a cyclic group having a steroid skeleton.

Among them, the cyclic aliphatic hydrocarbon group as R′²⁰¹ is preferably a group in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane, more preferably a group in which one hydrogen atom has been removed from a polycycloalkane, particularly preferably an adamantyl group or a norbornyl group, and most preferably an adamantyl group.

The linear or branched aliphatic hydrocarbon group which may be bonded to the alicyclic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms.

The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group is preferably a branched alkylene group, and specific examples thereof include alkylalkylene groups, for example, alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. The alkyl group in the alkylalkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

The cyclic hydrocarbon group as R′201 may contain a hetero atom such as a heterocyclic ring. Specific examples thereof include lactone-containing cyclic groups each represented by General Formulae (a2-r-1) to (a2-r-7), —SO₂—-containing cyclic groups each represented by General Formulae (a5-r-1) to (a5-r-4), and other heterocyclic groups each represented by Chemical Formulae (r-hr-1) to (r-hr-16).

Examples of the substituent of the cyclic group as R′²⁰¹ include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, and a nitro group.

The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

The halogen atom as the substituent is preferably a fluorine atom.

Examples of the above-described halogenated alkyl group as the substituent include a group in which part or all of hydrogen atoms in an alkyl group having 1 to 5 carbon atoms such as a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group have been substituted with the above-described halogen atom.

The carbonyl group as the substituent is a group that substitutes a methylene group (—CH₂—) constituting the cyclic hydrocarbon group.

Chain-like alkyl group which may have substituent:

The chain-like alkyl group as R′201 may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms.

The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and most preferably 3 to 10 carbon atoms. Specific examples thereof include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, and a 4-methylpentyl group.

Chain-like alkenyl group which may have substituent:

Such a chain-like alkenyl group as R′²⁰¹ may be linear or branched, preferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, still more preferably 2 to 4 carbon atoms, and particularly preferably 3 carbon atoms. Examples of the linear alkenyl group include a vinyl group, a propenyl group (an allyl group), and a butynyl group. Examples of the branched alkenyl group include a 1-methylvinyl group, a 2-methylvinyl group, a 1-methylpropenyl group, and a 2-methylpropenyl group.

Among the above, the chain-like alkenyl group is preferably a linear alkenyl group, more preferably a vinyl group or a propenyl group, and particularly preferably a vinyl group.

Examples of the substituent in the chain-like alkyl group or alkenyl group as R′²⁰¹, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, a nitro group, an amino group, a cyclic group as R′²⁰¹ or the like may be used.

As the cyclic group which may have a substituent, the chain-like alkyl group which may have a substituent, or the chain-like alkenyl group which may have a substituent, as R′²⁰¹, a group that is the same as the acid-dissociable group represented by above-described General Formula (a1-r-2) can be mentioned as the cyclic group which may have a substituent or the chain-like alkyl group which may have a substituent, in addition to the groups described above.

Among them, R′²⁰¹ is preferably a cyclic group which may have a substituent and more preferably a cyclic hydrocarbon group which may have a substituent. More specific examples thereof preferably include a phenyl group, a naphthyl group, a group in which one or more hydrogen atoms have been removed from a polycycloalkane, lactone-containing cyclic groups each represented by any one of General Formulae (a2-r-1) to (a2-r-7), and —SO₂—-containing cyclic groups each represented by any one of General Formulae (a5-r-1) to (a5-r-4).

In General Formulae (ca-1) to (ca-5), in a case where R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹ and R²¹² are bonded to each other to form a ring with a sulfur atom in the formula, these groups may be bonded to each other via a hetero atom such as a sulfur atom, an oxygen atom or a nitrogen atom, or a functional group such as a carbonyl group, —SO—, —SO₂—, —SO₃—, —COO—, —CONH—, or —N(R_(N))— (here, R_(N) represents an alkyl group having 1 to 5 carbon atoms). As the ring to be formed, a ring containing the sulfur atom in the formula in the ring skeleton thereof is preferably a 3- to 10-membered ring and particularly preferably a 5- to 7-membered ring including the sulfur atom. Specific examples of the ring to be formed include a thiophene ring, a thiazole ring, a benzothiophene ring, a benzothiophene ring, a dibenzothiophene ring, a 9H-thioxanthene ring, a thioxanthone ring, a thianthrene ring, a phenoxathiin ring, a tetrahydrothiophenium ring, and a tetrahydrothiopyranium ring.

R²⁰⁸ and R²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms and are preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In a case where R²⁰⁸ and R²⁰⁹ each independently represent an alkyl group, R²⁰⁸ and R²⁰⁹ may be bonded to each other to form a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a —SO₂—-containing cyclic group which may have a substituent.

Examples of the aryl group as R²¹⁰ include an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group or a naphthyl group is preferable.

The alkyl group as R²¹⁰, a chain-like or cyclic alkyl group having 1 to 30 carbon atoms is preferable.

The alkenyl group as R²¹⁰ preferably has 2 to 10 carbon atoms.

The —SO₂—-containing cyclic group which may have a substituent, as R²¹⁰, is preferably a “—SO₂—-containing polycyclic group”, and more preferably a group represented by General Formula (a5-r-1).

Each Y²⁰¹ independently represent an arylene group, an alkylene group, or an alkenylene group.

Examples of the arylene group as Y²⁰¹ include groups in which one hydrogen atom has been removed from an aryl group mentioned as the aromatic hydrocarbon group represented by R¹⁰¹ in General Formula (b-1) described above.

Examples of the alkylene group and alkenylene group as Y²⁰¹ include groups in which one hydrogen atom has been removed from the chain-like alkyl group or the chain-like alkenyl group as R¹⁰¹ in General Formula (b-1) described above.

In General Formula (ca-4), x represents 1 or 2.

W²⁰¹ represents an (x+1)-valent linking group, that is, a divalent or trivalent linking group.

The divalent linking group as W²⁰¹ is preferably a divalent hydrocarbon group which may have a substituent, and as examples thereof include the same divalent hydrocarbon group, which may have a substituent, as Ya²¹ in General Formula (a2-1). The divalent linking group as W²⁰¹ may be linear, branched or cyclic, and cyclic is more preferable. Among these, an arylene group having both terminals at which two carbonyl groups are combined is preferable. Examples of the arylene group include a phenylene group and a naphthylene group, and a phenylene group is particularly preferable.

Examples of the trivalent linking group as W²⁰¹ include a group in which one hydrogen atom has been removed from the above-described divalent linking group as W²⁰¹ and a group in which the divalent linking group has been bonded to another divalent linking group. The trivalent linking group as W²⁰¹ is preferably a group in which two carbonyl groups are bonded to an arylene group.

Specific examples of the suitable cation represented by General Formula (ca-1) include cations each represented by Chemical Formulae (ca-1-1) to (ca-1-70) shown below.

[In the formula, g1, g2, and g3 represent the numbers of repetitions, g1 is an integer in a range of 1 to 5, g2 is an integer in a range of 0 to 20, and g3 is an integer in a range of 0 to 20.]

[In the formula, R″²⁰¹ represents a hydrogen atom or a substituent, and examples of the substituent include the same substituent as that exemplified as the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² may have.]

Specific examples of suitable cations represented by General Formula (ca-2) include a diphenyliodonium cation and a bis(4-tert-butylphenyl)iodonium cation.

Specific examples of the suitable cations each represented by General Formula (ca-3) include cations each represented by General Formulae (ca-3-1) to (ca-3-6) shown below.

Specific examples of the suitable cations each represented by General Formula (ca-4) include cations each represented by General Formulae (ca-4-1) and (ca-4-2) shown below.

Specific examples of the suitable cations each represented by General Formula (ca-5) include cations each represented by General Formulae (ca-5-1) to (ca-5-3) shown below.

Among the above cations, as the cation moiety ((M′^(m+))_(l/m)), a cation represented by General Formula (ca-1) is preferable

In the resist composition according to the present embodiment, the component (B) may be used alone or in a combination of two or more kinds thereof.

In a case where the resist composition contains the component (B), the content of the component (B) in the resist composition is preferably less than 50 parts by mass, more preferably in a range of 1 to 40 parts by mass, and still more preferably in a range of 10 to 30 parts by mass with respect to 100 parts by mass of the component (A).

In a case where the content of the component (B) is set to be in the preferred range described above, pattern formation can be satisfactorily performed. Further, in a case where each component of the resist composition is dissolved in an organic solvent, the above range is preferable since a uniform solution is easily obtained and the storage stability of the resist composition is improved.

<<Base Component (D)>>

The resist composition according to the present embodiment may further contain, in addition to the component (A), a base component (a component (D)) that traps (that is, controls the acid diffusion) an acid generated from the component (B) upon exposure. The component (D) acts as a quencher (an acid diffusion-controlling agent) which traps the acid generated in the resist composition upon exposure.

Examples of the component (D) include a photodecomposable base (D1) having an acid diffusion controllability (hereinafter, referred to as a “component (D1)”) which is lost by the decomposition upon exposure and a nitrogen-containing organic compound (D2) (hereinafter, referred to as a “component (D2)”) which does not correspond to the component (D1). Among these, the photodecomposable base (the component (D1)) is preferable since it is easy to enhance the characteristics of high sensitivity, roughness reduction, and suppression of the occurrence of coating defects.

In Regard to Component (D1)

In a case where a resist composition containing the component (D1) is obtained, the contrast between the exposed portion and the unexposed portion of the resist film can be further improved at the time of the formation of a resist pattern.

The component (D1) is not particularly limited as long as it is decomposed upon exposure and loses the acid diffusion controllability. The component (D1) is preferably one or more compounds selected from the group consisting of a compound represented by General Formula (d1-1) (hereinafter, referred to as a “component (d1-1)”), a compound represented by General Formula (d1-2) (hereinafter, referred to as a “component (d1-2)”), and a compound represented by General Formula (d1-3) (hereinafter, referred to as a “component (d1-3)”).

At the exposed portion of the resist film, the components (d1-1) to (d1-3) are decomposed and then lose the acid diffusion controllability (basicity), and thus the components (d1-1) to (d1-3) cannot act as a quencher, whereas the components (d1-1) to (d1-3) act as a quencher at the unexposed portion of the resist film.

[In the formulae, Rd¹ to Rd⁴ represents cyclic groups which may have a substituent, chain-like alkyl groups which may have a substituent, or chain-like alkenyl groups which may have a substituent. Here, the carbon atom adjacent to the S atom as Rd² in General Formula (d1-2) has no fluorine atom bonded thereto. Yd¹ represents a single bond or a divalent linking group. m represents an integer of 1 or greater, and each M^(m+) independently represents an m-valent organic cation.]

{Component (d1-1)}

Anion Moiety

In General Formula (d1-1), Rd¹ represents a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent, and examples thereof include the same group as R′²⁰¹.

Among these, Rd¹ is preferably an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain-like alkyl group which may have a substituent. Examples of the substituent which these groups may have include a hydroxyl group, an oxo group, an alkyl group, an aryl group, a fluorine atom, a fluorinated alkyl group, lactone-containing cyclic groups each represented by any of General Formulae (a2-r-1) to (a2-r-7), an ether bond, an ester bond, and a combination thereof. In a case where an ether bond or an ester bond is included as the substituent, the substituent may be bonded via an alkylene group, and linking groups each represented by any of Formulae (y-a1-1) to (y-a1-5) are preferable as the substituent.

As the aromatic hydrocarbon group, a phenyl group, a naphthyl group, and a polycyclic structure (a polycyclic structure including a bicyclooctane skeleton and a ring structure other than the bicyclooctane skeleton) including a bicyclooctane skeleton can be suitably mentioned.

The aliphatic cyclic group is preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane.

The chain-like alkyl group preferably has 1 to 10 carbon atoms, and specific examples thereof include a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, or a decyl group, and a branched alkyl group such as a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, or a 4-methylpentyl group.

In a case where the chain-like alkyl group is a fluorinated alkyl group having a fluorine atom or a fluorinated alkyl group as a substituent, the fluorinated alkyl group preferably has 1 to 11 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbon atoms. The fluorinated alkyl group may contain an atom other than a fluorine atom. Examples of the atom other than a fluorine atom include an oxygen atom, a sulfur atom, and a nitrogen atom.

As Rd¹, a fluorinated alkyl group in which part or all of hydrogen atoms constituting a linear alkyl group have been substituted with a fluorine atom is preferable, and a fluorinated alkyl group in which all of the hydrogen atoms constituting a linear alkyl group have been substituted with a fluorine atom (a linear perfluoroalkyl group) is particularly preferable.

Specific examples of the preferred anion moiety for the component (d1-1) are shown below.

Cation Moiety

In General Formula (d1-1), M^(m+) represents an m-valent organic cation.

The organic cations of M^(m+) are suitably the same as those each represented by General Formulae (ca-1) to (ca-5), the cations each represented by General Formula (ca-1) are preferable, and cations each represented by Formulae (ca-1-1) to (ca-1-70) are more preferable.

The component (d1-1) may be used alone or in a combination of two or more kinds thereof.

{Component (d1-2)}

Anion Moiety

In General Formula (d1-2), Rd² represents a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent, and examples thereof include the same group as R′²⁰¹.

Here, the carbon atom adjacent to the S atom in Rd² has no fluorine atom bonded thereto (the carbon atom adjacent to the S atom in Rd² is not substituted with a fluorine atom). As a result, the anion of the component (d1-2) becomes an appropriately weak acid anion, thereby improving the quenching ability of the component (D).

Rd² is preferably a chain-like alkyl group which may have a substituent or an aliphatic cyclic group which may have a substituent. The chain-like alkyl group preferably has 1 to 10 carbon atoms and more preferably 3 to 10 carbon atoms. The aliphatic cyclic group is more preferably a group (which may have a substituent) in which one or more hydrogen atoms have been removed from adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, or the like; and a group in which one or more hydrogen atoms have been removed from camphor or the like.

The hydrocarbon group as Rd² may have a substituent. Examples of the substituent include the same substituent as that which the hydrocarbon group (an aromatic hydrocarbon group, an aliphatic cyclic group, or a chain-like alkyl group) as Rd¹ in General Formula (d1-1) may have.

Specific examples of the preferred anion moiety for the component (d1-2) are shown below.

Cation Moiety

In General Formula (d1-2), M^(m+) represents an m-valent organic cation and is the same as M^(m+) in General Formula (d1-1).

The component (d1-2) may be used alone or in a combination of two or more kinds thereof.

{Component (d1-3)}

Anion Moiety

In General Formula (d1-3), Rd³ represents a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent, examples thereof include the same groups as R′²⁰¹ and a cyclic group containing a fluorine atom, a chain-like alkyl group, or a chain-like alkenyl group is preferable. Among them, a fluorinated alkyl group is preferable, and the same fluorinated alkyl group as that described above as Rd¹ is more preferable.

In General Formula (d1-3), Rd⁴ represents a cyclic group which may have a substituent, a chain-like alkyl group which may have a substituent, or a chain-like alkenyl group which may have a substituent, and examples thereof include the same group as R′²⁰¹.

Among them, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an alkenyl group which may have a substituent, or a cyclic group which may have a substituent is preferable.

The alkyl group as Rd⁴ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. A part of hydrogen atoms in the alkyl group as Rd⁴ may be substituted with a hydroxyl group, a cyano group, or the like.

The alkoxy group as Rd⁴ is preferably an alkoxy group having 1 to 5 carbon atoms, and specific examples of the alkoxy group having 1 to 5 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, and a tert-butoxy group. Among these, a methoxy group and an ethoxy group are preferable.

Examples of the alkenyl group as Rd⁴ include the same group as R′²⁰¹, and a vinyl group, a propenyl group (an allyl group), a 1-methylpropenyl group, or a 2-methylpropenyl group is preferable. These groups may have an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms as a substituent.

Examples of the cyclic group as Rd⁴ include the same cyclic group as R′²⁰¹ and an alicyclic group in which one or more hydrogen atoms have been removed from a cycloalkane such as cyclopentane, cyclohexane, adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane, or an aromatic group such as a phenyl group or a naphthyl group is preferable. In a case where Rd⁴ represents an alicyclic group, the resist composition can be satisfactorily dissolved in an organic solvent, thereby improving the lithography characteristics. In a case where Rd⁴ is an aromatic group, the resist composition is excellent in light absorption efficiency and thus has good sensitivity and lithography characteristics in the lithography using EUV or the like as a light source for exposure.

In General Formula (d1-3), Yd¹ represents a single bond or a divalent linking group.

The divalent linking group as Yd¹ is not particularly limited, and examples thereof include a divalent hydrocarbon group (an aliphatic hydrocarbon group or an aromatic hydrocarbon group) which may have a substituent and a divalent linking group containing a hetero atom. The divalent linking groups are the same as those described above as the divalent hydrocarbon group which may have a substituent and the divalent linking group containing a hetero atom described above as the divalent linking group as Ya²¹ in General Formula (a2-1).

As Yd¹, a carbonyl group, an ester bond, an amide bond, an alkylene group, or a combination of these is preferable. As the alkylene group, a linear or branched alkylene group is more preferable, and a methylene group or an ethylene group is still more preferable.

Specific examples of the preferred anion moiety for the component (d1-3) are shown below.

Cation Moiety

In General Formula (d1-3), M^(m+) represents an m-valent organic cation and is the same as M^(m+) in General Formula (d1-1).

The component (d1-3) may be used alone or in a combination of two or more kinds thereof.

As the component (D1), only one of the above-described components (d1-1) to (d1-3) or a combination of two or more kinds thereof may be used.

In a case where the resist composition contains the component (D1), the content of the component (D1) in the resist composition is preferably less than 0.5 to 20 parts by mass, more preferably in a range of 1 to 15 parts by mass, and still more preferably in a range of 3 to 10 parts by mass with respect to 100 parts by mass of the component (A).

In a case where the content of the component (D1) is equal to or greater than the preferred lower limit, excellent lithography characteristics and an excellent resist pattern shape are easily obtained. On the other hand, in a case where the content of the component (D1) is equal to or lower than the upper limit, the sensitivity can be maintained satisfactorily and the throughput is also excellent.

Method of Producing Component (D1):

The methods of producing the components (d1-1) and (d1-2) are not particularly limited, and the components (d1-1) and (d1-2) can be produced by conventionally known methods.

Further, the method of producing the component (d1-3) is not particularly limited, and the component (d1-3) can be produced in the same manner as disclosed in United States Patent Application, Publication No. 2012-0149916.

In Regard to Component (D2)

The component (D) may contain a nitrogen-containing organic compound component (hereinafter, referred to as a “component (D2)”) which does not correspond to the above-mentioned component (D1).

The component (D2) is not particularly limited as long as it acts as an acid diffusion controlling agent and does not correspond to the component (D1), and any known compound may be used. Among the above, aliphatic amines are preferable, and among the aliphatic amines, a secondary aliphatic amine or a tertiary aliphatic amine is more preferable.

An aliphatic amine is an amine having one or more aliphatic groups, and the aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include an amine in which at least one hydrogen atom of ammonia (NH₃) has been substituted with an alkyl group or hydroxyalkyl group having 12 or fewer carbon atoms (alkyl amines or alkyl alcohol amines) and a cyclic amine.

Specific examples of alkyl amines and alkyl alcohol amines include monoalkyl amines such as n-hexyl amine, n-heptyl amine, n-octyl amine, n-nonyl amine, and n-decyl amine; dialkyl amines such as diethyl amine, di-n-propyl amine, di-n-heptyl amine, di-n-octyl amine, and dicyclohexyl amine; trialkyl amines such as trimethyl amine, triethyl amine, tri-n-propyl amine, tri-n-butyl amine, tri-n-hexyl amine, tri-n-pentyl amine, tri-n-heptyl amine, tri-n-octyl amine, tri-n-nonyl amine, tri-n-decyl amine, and tri-n-dodecyl amine; and alkyl alcohol amines such as diethanol amine, triethanol amine, diisopropanol amine, triisopropanol amine, di-n-octanol amine, and tri-n-octanol amine. Among these, trialkyl amines of 5 to 10 carbon atoms are preferable, and tri-n-pentyl amine and tri-n-octyl amine are particularly preferable.

Examples of the cyclic amine include heterocyclic compounds containing a nitrogen atom as a hetero atom. The heterocyclic compound may be a monocyclic compound (aliphatic monocyclic amine), or a polycyclic compound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, and specific examples thereof include 1, 5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and 1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines include tris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine, tris [2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanol amine triacetate, and triethanol amine triacetate is preferable.

In addition, as the component (D2), an aromatic amine may be used.

Examples of aromatic amines include 4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole, and derivatives thereof, tribenzylamine, 2,6-diisopropylaniline, and N-tert-butoxycarbonylpyrrolidine.

The component (D2) may be used alone or in a combination of two or more kinds thereof.

In a case where the resist composition contains the component (D2), the content of the component (D2) in the resist composition is typically in a range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the component (A). By setting the content within the above range, the resist pattern shape, the post-exposure temporal stability, and the like are improved.

<<At Least One Compound (E) Selected from the Group Consisting of Organic Carboxylic Acid, Phosphorus Oxo Acid, and Derivatives Thereof>>

For the purpose of preventing any deterioration in sensitivity, and improving the resist pattern shape and the post-exposure temporal stability, the resist composition according to the present embodiment may contain, as an optional component, at least one compound (E) (hereinafter referred to as a component (E)) selected from the group consisting of an organic carboxylic acid, and a phosphorus oxo acid and a derivative thereof.

Examples of suitable organic carboxylic acids include acetic acid, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.

Examples of phosphorus oxo acid include phosphoric acid, phosphonic acid, and phosphinic acid. Among these, phosphonic acid is particularly preferable.

Examples of phosphorus oxo acid derivatives include esters in which a hydrogen atom in the above-described oxo acids is substituted with a hydrocarbon group.

Examples of the hydrocarbon group include an alkyl group having 1 to 5 carbon atoms and an aryl group having 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esters such as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esters such as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonic acid, diphenyl phosphonate, and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esters and phenylphosphinic acid.

In the resist composition according to the present embodiment, the component (E) may be used alone or in a combination of two or more kinds thereof.

In a case where the resist composition contains the component (E), the content of the component (E) is typically in a range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the component (A).

<<Fluorine Additive Component (F)>>

The resist composition according to the present embodiment may further include a fluorine additive component (hereinafter, referred to as a “component (F)”) in order to impart water repellency to the resist film or to improve lithography characteristics.

As the component (F), a fluorine-containing polymer compound described in Japanese Unexamined Patent Application, First Publication No. 2010-002870, Japanese Unexamined Patent Application, First Publication No. 2010-032994, Japanese Unexamined Patent Application, First Publication No. 2010-277043, Japanese Unexamined Patent Application, First Publication No. 2011-13569, and Japanese Unexamined Patent Application, First Publication No. 2011-128226 can be mentioned.

Specific examples of the component (F) include polymers having a constitutional unit (f1) represented by General Formula (f1-1) shown below. This polymer is preferably a polymer (homopolymer) consisting of a constitutional unit (f1) represented by General Formula (f1-1) shown below; a copolymer of the constitutional unit (f1) and the constitutional unit (a1); and a copolymer of the constitutional unit (f1), a constitutional unit derived from acrylic acid or methacrylic acid, and the above-described constitutional unit (a1). As the constitutional unit (a1) to be copolymerized with the constitutional unit (f1), a constitutional unit derived from 1-ethyl-1-cyclooctyl (meth)acrylate and a constitutional unit derived from 1-methyl-1-adamantyl (meth)acrylate are preferable.

[In the formula, R has the same definition as described above. Rf¹⁰² and Rf¹⁰³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, and Rf¹⁰² and R¹⁰³ may be the same as or different from each other. nf¹ represents an integer in a range of 0 to 5 and Rf¹⁰¹ represents an organic group containing a fluorine atom.]

In General Formula (f1-1), R bonded to the carbon atom at the α-position has the same definition as described above. R is preferably a hydrogen atom or a methyl group.

In General Formula (f1-1), the halogen atom of Rf¹⁰² and Rf¹⁰³ is preferably a fluorine atom. Examples of the alkyl group having 1 to 5 carbon atoms as Rf¹⁰² and Rf¹⁰³ include those described above as the alkyl group having 1 to 5 carbon atoms as R, and a methyl group or an ethyl group is preferable. Specific examples of the halogenated alkyl group having 1 to 5 carbon atoms as Rf¹⁰² and Rf¹⁰³ include groups in which part or all of hydrogen atoms of the above-described alkyl groups of 1 to 5 carbon atoms have been substituted with a halogen atom. The halogen atom is preferably a fluorine atom. Among these examples, as Rf¹⁰² and Rf¹⁰³, a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 5 carbon atoms is preferable, and a hydrogen atom, a fluorine atom, a methyl group, or an ethyl group is more preferable.

In General Formula (f1-1), nf¹ represents an integer in a range of 0 to 5, preferably an integer in a range of 0 to 3, and more preferably an integer of 1 or 2.

In General Formula (f1-1), Rf¹⁰¹ represents an organic group containing a fluorine atom and is preferably a hydrocarbon group containing a fluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branched, or cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

In addition, in the hydrocarbon group containing a fluorine atom, 25% or more of the hydrogen atoms in the hydrocarbon group are preferably fluorinated, more preferably 50% or more are fluorinated, and particularly preferably 60% or more are fluorinated since the hydrophobicity of the resist film at the time of dipping exposure increases.

Among them, Rf¹⁰¹ is preferably a fluorinated hydrocarbon group having 1 to 6 carbon atoms, more preferably a trifluoromethyl group, and particularly preferably —CH₂—CF₃, —CH₂—CF₂—CF₃, or —CH(CF₃)₂, —CH₂—CH₂—CF₃, or —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃.

The weight-average molecular weight (Mw) (based on the polystyrene-equivalent value determined by gel permeation chromatography) of the component (F) is preferably in a range of 1,000 to 50,000, more preferably in a range of 5,000 to 40,000, and most preferably in a range of 10,000 to 30,000. In a case where the weight-average molecular weight is equal to or lower than the upper limit value of this range, the resist composition exhibits sufficiently satisfactory solubility in a solvent for a resist to be used as a resist. On the other hand, in a case where the weight-average molecular weight is equal to or greater than the lower limit value of this range, water repellency of the resist film is excellent.

Further, the dispersity (Mw/Mn) of the component (F) is preferably in a range of 1.0 to 5.0, more preferably in a range of 1.0 to 3.0, and most preferably in a range of 1.0 to 2.5.

In the resist composition according to the present embodiment, the component (F) may be used alone or in a combination of two or more kinds thereof.

In a case where the resist composition contains the component (F), the content of the component (F) is typically at a proportion in a range of 0.5 to 10 parts by mass, with respect to 100 parts by mass of the component (A).

<<Organic Solvent Component (S)>>

The resist composition according to the present embodiment may be produced by dissolving the resist materials in an organic solvent component (hereinafter, referred to as a “component (S)”).

The component (S) may be any organic solvent which can dissolve each of the components to be used to obtain a uniform solution, and optional organic solvent can be suitably selected from those which are conventionally known as solvents for a chemical amplification-type resist composition and then used.

Examples of the component (S) include lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such as ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol; compounds having an ester bond, such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, and dipropylene glycol monoacetate; polyhydric alcohol derivatives including compounds having an ether bond, such as a monoalkyl ether (such as monomethyl ether, monoethyl ether, monopropyl ether or monobutyl ether) or monophenyl ether of any of these polyhydric alcohols or compounds having an ester bond (among these, propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether (PGME) are preferable); cyclic ethers such as dioxane; esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and ethyl ethoxypropionate; aromatic organic solvents such as anisole, ethylbenzyl ether, cresylmethyl ether, diphenyl ether, dibenzyl ether, phenetole, butylphenyl ether, ethyl benzene, diethyl benzene, pentyl benzene, isopropyl benzene, toluene, xylene, cymene and mesitylene; and dimethylsulfoxide (DMSO).

In the resist composition according to the present embodiment, the component (S) may be used alone or as a mixed solvent of two or more kinds thereof. Among these, PGMEA, PGME, γ-butyrolactone, EL, and cyclohexanone are preferable.

Further, a mixed solvent obtained by mixing PGMEA with a polar solvent is also preferable as the component (S). The blending ratio (mass ratio) of the mixed solvent can be suitably determined, taking into consideration the compatibility of the PGMEA with the polar solvent, but is preferably in a range of 1:9 to 9:1 and more preferably in a range of 2:8 to 8:2.

More specifically, in a case where EL or cyclohexanone is blended as the polar solvent, the PGMEA:EL or cyclohexanone mass ratio is preferably in a range of 1:9 to 9:1 and more preferably in a range of 2:8 to 8:2. Alternatively, in a case where PGME is blended as the polar solvent, the PGMEA:PGME mass ratio is preferably in a range of 1:9 to 9:1, more preferably in a range of 2:8 to 8:2, and still more preferably in a range of 3:7 to 7:3. Furthermore, a mixed solvent of PGMEA, PGME, and cyclohexanone is also preferable.

Further, the component (S) is also preferably a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone. In this case, as the mixing ratio, the mass ratio of the former to the latter is preferably in a range of 70:30 to 95:5.

The amount of the component (S) to be used is not particularly limited and is suitably set, depending on a thickness of a film to be coated, to a concentration at which the component (S) can be applied onto a substrate or the like. Generally, the component (S) is used such that the solid content concentration of the resist composition is in a range of 0.1% to 20% by mass and preferably in a range of 0.2% to 15% by mass.

As desired, other miscible additives can also be added to the resist composition according to the present embodiment. For example, for improving the performance of the resist film, an additive resin, a dissolution inhibitor, a plasticizer, a stabilizer, a colorant, a halation prevention agent, and a dye can be suitably contained therein.

After dissolving the resist material in the component (S), the resist composition according to the present embodiment may be subjected to removal of impurities and the like by using a porous polyimide film, a porous polyamideimide film, or the like. For example, the resist composition may be filtered using a filter made of a porous polyimide film, a filter made of a porous polyamideimide film, or a filter made of a porous polyimide film and a porous polyamideimide film. Examples of the porous polyimide film and the porous polyamideimide film include those described in Japanese Unexamined Patent Application, First Publication No. 2016-155121.

The resist composition according to the present embodiment described above contains a resin component (A1) having the above-described constitutional unit (a01).

In the constitutional unit (a01), the bond between the oxygen atom of the carbonyloxy group (C(═O)—O—) and C^(t) in General Formula (a01-1) is cleaved by action of acid, whereby a carbocation is generated. The constitutional unit (a01) has a carbon-carbon double bond and has an electron-donating group (a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent) as a substituent at the double bond moiety. For this reason, the electrical bias of the positive charge of the carbocation to be generated can be further suppressed, and the carbocation to be generated can be more stabilized. This promotes the deprotection reaction of the constitutional unit (a01). In addition, an electron-donating group is introduced, as a substituent, into the double bond moiety of the constitutional unit (a01), and thus the reactivity is significantly increased and the effect on physical properties on the resin component (A1) having the constitutional unit (a01) is minimized.

As a result, the resist composition according to the present embodiment containing the resin component (A1) having the constitutional unit (a01) can cause a sufficient deprotection reaction to occur with a small irradiation dose of the light source for exposure, and it is possible to generate the dissolution contrast between the exposed portion and the unexposed portion without affecting the unexposed portion.

As described above, according to the resist composition according to the present embodiment, it is possible to further increase the sensitivity and further improve the lithography characteristics (particularly, the exposure margin).

Further, the resist composition according to the present embodiment is a resist composition containing the above-described resin component (A1). In a case where a 1:1 LS pattern having a line width of 50 nm is formed using the resist composition, the optimum exposure amount Eop (μC/cm²) with which the above LS pattern is formed is obtained, and the irradiation dose is reduced from the optimum exposure amount Eop so that the space dimension is reduced, the minimum exposure amount with which a pattern can be formed without causing defects such as scum and bridge is denoted by E0, and in a case where the irradiation dose is increased from the optimum exposure amount Eop so that the space dimension is increased, the maximum exposure amount with which a pattern can be formed without causing defects such as collapse and disconnection is denoted by E1, the resist composition has the characteristics that the ratio (E1/E0) of the minimum exposure amount E0 to the maximum exposure amount E1 is preferably 2.0 or more, more preferably 2.5 or more, still more preferably 2.6 or more, and particularly preferably 3.0 or more.

The upper limit value of the ratio (E1/E0) between the minimum exposure amount E0 and the maximum exposure amount E1 is, for example, 5.0.

Specific examples of the method for forming a 1:1 LS pattern having a line width of 50 nm include a method in which a post-apply baking (PAB) treatment is carried out at a temperature of 110° C. for 60 seconds to form a resist film having a thickness of 30 nm, drawing (exposure) is performed on the resist film by using an electron beam lithography apparatus JEOL-JBX-9300FS (manufactured by JEOL Ltd.), with the target size being set to a 1:1 line-and-space pattern of a line width of 50 nm, at an accelerating voltage of 100 kV, a post-exposure baking (PEB) treatment is performed on the resist film at 110° C. for 60 seconds, alkali development is performed at 23° C. for 60 seconds using a 2.38% by mass tetramethylammonium hydroxide (TMAH) aqueous solution “NMD-3” (trade name, manufactured by TOKYO OHKA KOGYO CO., LTD.), and rinsing is performed for 15 seconds using pure water.

(Method of Forming Resist Pattern)

A method of forming a resist pattern according to the second aspect according to the present invention is a method including a step of forming a resist film on a support using the resist composition according to the first aspect of the present embodiment described above, a step of exposing the resist film, and a step of developing the exposed resist film to form a resist pattern.

Examples of one embodiment of such a method of forming a resist pattern include a method of forming a resist pattern performed as described below.

First, the resist composition of the above-described embodiment is applied onto a support with a spinner or the like, and a baking (post-apply baking (PAB)) treatment is performed, for example, at a temperature condition in a range of 80° C. to 150° C. for 40 to 120 seconds, preferably for 60 to 90 seconds to form a resist film.

Following the selective exposure performed on the resist film by, for example, exposure through a mask (mask pattern) having a predetermined pattern formed on the mask by using a lithography apparatus such as an electron beam lithography apparatus or an EUV lithography apparatus, or direct irradiation of the resist film for drawing with an electron beam without using a mask pattern, baking treatment (post-exposure baking (PEB)) is performed, for example, under a temperature condition in a range of 80° C. to 150° C. for 40 to 120 seconds and preferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment. The developing treatment is performed using an alkali developing solution in a case of an alkali developing process, and a developing solution containing an organic solvent (organic developing solution) in a case of a solvent developing process.

After the developing treatment, it is preferable to conduct a rinse treatment. As the rinse treatment, water rinsing using pure water is preferable in a case of an alkali developing process, and rinsing using a rinse liquid containing an organic solvent is preferable in a case of a solvent developing process.

In a case of a solvent developing process, after the developing treatment or the rinsing, the developing solution or the rinse liquid remaining on the pattern can be removed by a treatment using a supercritical fluid.

After the developing treatment or the rinse treatment, drying is conducted. As desired, baking treatment (post-baking) can be performed following the developing treatment.

In this manner, a resist pattern can be formed.

The support is not specifically limited and a conventionally known support can be used. For example, substrates for electronic components, and such substrates having a predetermined wiring patterns formed thereon can be used. Specific examples of the material of the substrate include metals such as silicon wafer, copper, chromium, iron and aluminum; and glass. Suitable materials for the wiring pattern include copper, aluminum, nickel, and gold.

Further, as the support, any support having the above-described substrate on which an inorganic and/or organic film is provided may be used. As the inorganic film, an inorganic antireflection film (inorganic BARC) can be used. Examples of the organic film include an organic antireflection film (organic BARC) and an organic film such as a lower-layer organic film used in a multilayer resist method.

Here, the multilayer resist method is a method in which at least one layer of an organic film (lower-layer organic film) and at least one layer of a resist film (upper-layer resist film) are provided on a substrate, and a resist pattern formed on the upper-layer resist film is used as a mask to conduct patterning of the lower-layer organic film. This method is considered as being capable of forming a pattern with a high aspect ratio. More specifically, in the multilayer resist method, a desired thickness can be ensured by the lower-layer organic film, and as a result, the thickness of the resist film can be reduced, and an extremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is classified into a method in which a double-layer structure consisting of an upper-layer resist film and a lower-layer organic film is formed (double-layer resist method), and a method in which a multilayer structure having at least three layers consisting of an upper-layer resist film, a lower-layer organic film and at least one intermediate layer (thin metal film or the like) provided between the upper-layer resist film and the lower-layer organic film (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited and the exposure can be performed using radiation such as an ArF excimer laser, a KrF excimer laser, an F₂ excimer laser, extreme ultraviolet (EUV) rays, vacuum ultraviolet (VUV) rays, electron beams (EB), X-rays, or soft X-rays. The resist composition is highly useful for a KrF excimer laser, an ArF excimer laser, EB, or EUV, more useful for an ArF excimer laser, EB or EUV, and particularly useful for EB or EUV. That is, the method of forming a resist pattern according to the present embodiment is a particularly useful method in a case where the step of exposing the resist film includes an operation of exposing the resist film to extreme ultraviolet (EUV) rays or electron beams (EB).

The exposure of the resist film can be a general exposure (dry exposure) performed in air or an inert gas such as nitrogen, or liquid immersion exposure (liquid immersion lithography).

In liquid immersion lithography is an exposure method in which the region between the resist film and the lens at the lowermost position of the lithography apparatus is pre-filled with a solvent (liquid immersion medium) that has a larger refractive index than the refractive index of air, and the exposure (dipping exposure) is performed in this state.

As the liquid immersion medium, a solvent that exhibits a refractive index larger than the refractive index of air but smaller than the refractive index of the resist film to be exposed is preferable. The refractive index of the solvent is not particularly limited as long as it satisfies the above-described requirements.

Examples of the solvent which exhibits a refractive index that is larger than the refractive index of air but smaller than the refractive index of the resist film include water, fluorine-based inert liquids, silicone-based solvents, and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquids containing a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃, C₄F₉OC₂H₅, or C₅H₃F₇ as the main component, and the boiling point is preferably in a range of 700 to 180° C. and more preferably in a range of 80° to 160° C. A fluorine-based inert liquid having a boiling point in the above-described range is advantageous in that removing the medium used in the liquid immersion after the exposure can be preferably performed by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which all of the hydrogen atoms of the alkyl group are substituted with a fluorine atom is particularly preferable. Examples of these perfluoroalkyl compounds include perfluoroalkyl ether compounds and perfluoroalkyl amine compounds.

Specifically, an example of a suitable perfluoroalkyl ether compound is perfluoro(2-butyl-tetrahydrofuran) (boiling point of 102° C.), and an example of a suitable perfluoroalkyl amine compound is perfluorotributyl amine (boiling point of 174° C.).

As the liquid immersion medium, water is preferable in terms of cost, safety, environment, and versatility.

Examples of the alkali developing solution used for a developing treatment in an alkali developing process include a 0.1% to 10% by mass aqueous solution of tetramethylammonium hydroxide (TMAH).

As the organic solvent contained in the organic developing solution, which is used for a developing treatment in a solvent developing process, any one of the conventionally known organic solvents capable of dissolving the component (A) (component (A) prior to exposure) can be suitably selected from the conventionally known organic solvents. Specific examples of the organic solvent include polar solvents such as a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, a nitrile-based solvent, an amide-based solvent, and an ether-based solvent, and hydrocarbon-based solvents.

A ketone-based solvent is an organic solvent containing C—C(═O)—C in the structure thereof. An ester-based solvent is an organic solvent containing C—C(═O)—O—C in the structure thereof. An alcohol-based solvent is an organic solvent containing an alcoholic hydroxyl group in the structure thereof. An “alcoholic hydroxyl group” indicates a hydroxyl group bonded to a carbon atom of an aliphatic hydrocarbon group. A nitrile-based solvent is an organic solvent containing a nitrile group in the structure thereof. An amide-based solvent is an organic solvent containing an amide group in the structure thereof. An ether-based solvent is an organic solvent containing C—O—C in the structure thereof.

Some organic solvents have a plurality of the functional groups which characterize the above-described solvents in the structure thereof. In such a case, the organic solvent can be classified as any type of solvent having a characteristic functional group. For example, diethylene glycol monomethyl ether can be classified as an alcohol-based solvent or an ether-based solvent.

A hydrocarbon-based solvent consists of a hydrocarbon which may be halogenated and does not have any substituent other than a halogen atom. The halogen atom is preferably a fluorine atom.

Among the above, the organic solvent contained in the organic developing solution is preferably a polar solvent and more preferably a ketone-based solvent, an ester-based solvent, or a nitrile-based solvent.

Examples of ketone-based solvent include 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone, isophorone, propylenecarbonate, γ-butyrolactone and methylamyl ketone (2-heptanone). Among these examples, the ketone-based solvent is preferably methylamyl ketone (2-heptanone).

Examples of the ester-based solvent include methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethyl methoxyacetate, ethyl ethoxyacetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monophenyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, 4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, propyl lactate, ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl-3-methoxypropionate, ethyl-3-methoxypropionate, ethyl-3-ethoxypropionate, and propyl-3-methoxypropionate. Among these, the ester-based solvent is preferably butyl acetate.

Examples of the nitrile-based solvent include acetonitrile, propionitrile, valeronitrile, and butyronitrile.

As desired, the organic developing solution may have a conventionally known additive blended. Examples of the additive include surfactants. The surfactant is not particularly limited, and for example, an ionic or non-ionic fluorine-based and/or a silicone-based surfactant can be used. As the surfactant, a non-ionic surfactant is preferable, and a non-ionic fluorine-based surfactant or a non-ionic silicone-based surfactant is more preferable.

In a case where a surfactant is blended, the amount of the surfactant to be blended is typically in a range of 0.001% to 5% by mass, preferably in a range of 0.005% to 2% by mass, and more preferably in a range of 0.01% to 0.5% by mass with respect to the total amount of the organic developing solution.

The developing treatment can be performed by a conventionally known developing method. Examples thereof include a method in which the support is immersed in the developing solution for a predetermined time (a dip method), a method in which the developing solution is cast upon the surface of the support by surface tension and maintained for a predetermined period (a puddle method), a method in which the developing solution is sprayed onto the surface of the support (spray method), and a method in which a developing solution is continuously ejected from a developing solution ejecting and applying nozzle and applied onto a support which is scanned at a constant rate while being rotated at a constant rate (dynamic dispense method).

As the organic solvent contained in the rinse liquid used in the rinse treatment after the developing treatment in a case of a solvent developing process, an organic solvent hardly dissolving the resist pattern can be suitably selected and used, among the organic solvents mentioned as organic solvents that are used for the organic developing solution. In general, at least one kind of solvent selected from the group consisting of a hydrocarbon-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, an amide-based solvent, and an ether-based solvent is used. Among these, at least one kind of solvent selected from the group consisting of a hydrocarbon-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, and an amide-based solvent is preferable, at least one kind of solvent selected from the group consisting of an alcohol-based solvent and an ester-based solvent is more preferable, and an alcohol-based solvent is particularly preferable.

The alcohol-based solvent used for the rinse liquid is preferably a monohydric alcohol of 6 to 8 carbon atoms, and the monohydric alcohol may be linear, branched, or cyclic. Specific examples thereof include 1-hexanol, 1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol, 3-heptanol, 3-octanol, 4-octanol, and benzyl alcohol. Among these, 1-hexanol, 2-heptanol, and 2-hexanol are preferable, and 1-hexanol and 2-hexanol are more preferable.

As the organic solvent, one kind of solvent may be used alone, or two or more kinds of solvents may be used in combination. Further, an organic solvent other than the above-described examples or water may be mixed thereto. However, in consideration of the development characteristics, the amount of water to be blended in the rinse liquid is preferably 30% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and most preferably 3% by mass or less with respect to the total amount of the rinse liquid.

A conventionally known additive can be blended with the rinse liquid as necessary. Examples of the additive include surfactants. Examples of the surfactant include the same surfactants as those described above, the surfactant is preferably a non-ionic surfactant and more preferably a non-ionic fluorine-based surfactant or a non-ionic silicone-based surfactant.

In a case where a surfactant is blended, the amount of the surfactant to be blended is typically in a range of 0.001% to 5% by mass, preferably in a range of 0.005% to 2% by mass, and more preferably in a range of 0.01% to 0.5% by mass with respect to the total amount of the rinse liquid.

The rinse treatment using a rinse liquid (washing treatment) can be performed by a conventionally known rinse method. Examples of the rinse treatment method include a method in which the rinse liquid is continuously ejected and applied onto the support while rotating it at a constant rate (rotational coating method), a method in which the support is immersed in the rinse liquid for a predetermined time (dip method), and a method in which the rinse liquid is sprayed onto the surface of the support (spray method).

According to the method of forming a resist pattern according to the present embodiment described above, since the resist composition according to the embodiment described above is used, it is possible to obtain high sensitivity and to stably form a resist pattern (having a broad exposure margin) even in a case where the irradiation dose of the light source for exposure varies.

EXAMPLES

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

Synthesis Example 1 Synthesis Example of Polymer Compound (A1-1)

15.0 g of a monomer (a01-1m-1), 14.8 g of a monomer (a10-1-1 pre), and 1.24 g of azobis (isobutyric acid) dimethyl (V-601) as a polymerization initiator were dissolved in 60.5 g of methyl ethyl ketone (MEK), and the mixture was heated to 85° C. in a nitrogen atmosphere and stirred for 5 hours. Then, 13.8 g of acetic acid and 271 g of methanol were added to the reaction solution, and a deprotection reaction was carried out at 30° C. for 8 hours. After completion of the reaction, the obtained reaction solution was precipitated in 2,500 g of heptane, followed by washing. The obtained white solid was filtered and dried under reduced pressure overnight to obtain the target polymer compound (A1-1).

As a result of a GPC measurement to determine the weight-average molecular weight (Mw) in terms of standard polystyrene, the obtained polymer compound (A1-1) had a weight-average molecular weight of 5,500 and a polydispersity (Mw/Mn) of 1.57. The copolymerization compositional ratio (the ratio (the molar ratio) between constitutional units each derived from the monomer) determined by ¹³C-NMR was l/m=50/50.

Synthesis Examples 2 to 15

Polymer compounds (A1-2) to (A1-10), (A2-1) to (A2-5) having the compositional ratios shown in Table 1 were synthesized using the compounds shown below in the same manner as in Synthesis Example 1.

With respect to the obtained polymer compounds, the copolymerization compositional ratio (the ratio (molar ratio) between constitutional units, each of which is derived from a monomer) in the polymer compound, which was determined by ¹³C-NMR, the weight-average molecular weight (Mw) in terms of standard polystyrene, which was determined by GPC measurement, and the polydispersity (Mw/Mn) are shown together in Table 1.

The constitutional units represented by Chemical Formula (a10-1-1) and the constitutional unit represented by Chemical Formula (a10-1-2), which constitute the above-described copolymer, are each constitutional units derived from a monomer represented by Chemical Formula (a10-1-1 pre) and a constitutional unit derived from a monomer represented by Chemical Formula (a10-1-2 pre).

TABLE 1 Weight-average Polymer Copolymerization compositional ratio molecular weight Polydispersity compound (molar ratio) of polymer compound (Mw) (Mw/Mn) Synthesis (A1-1) (a01-1m-1)/(a10-1-1) = 50/50 5500 1.57 Example 1 Synthesis (A1-2) (a01-1m-2)/(a10-1-1) = 50/50 5300 1.51 Example 2 Synthesis (A1-3) (a01-1m-5)/(a10-1-1) = 50/50 6100 1.56 Example 3 Synthesis (A1-4) (a01-1m-6)/(a10-1-1) = 50/50 5600 1.55 Example 4 Synthesis (A1-5) (a01-1m-1)/(a10-1-1)/(a8-1-01) = 50/40/10 6600 1.65 Example 5 Synthesis (A1-6) (a01-1m-3)/(a10-1-1)/(a8-1-01) = 50/40/10 7000 1.66 Example 6 Synthesis (A1-7) (a01-1m-1)/(a10-1-2) = 40/60 5100 1.58 Example 7 Synthesis (A1-8) (a01-1m-4)/(a10-1-2) = 40/60 5400 1.60 Example 8 Synthesis (A1-9) (a01-1m-1)/(a2-1) = 60/40 7400 1.68 Example 9 Synthesis (A1-10) (a01-1m-7)/(a2-1)/(a3-1) = 40/40/20 8200 1.70 Example 10 Synthesis (A2-1) (a1-1)/(a10-1-1) = 50/50 5500 1.54 Example 11 Synthesis (A2-2) (a1-2)/(a10-1-1)/(a8-1-01) = 50/40/10 7200 1.69 Example 12 Synthesis (A2-3) (a1-2)/(a10-1-2) = 40/60 5900 1.61 Example 13 Synthesis (A2-4) (a1-1)/(a2-1) = 60/40 7500 1.66 Example 14 Synthesis (A2-5) (a1-3)/(a2-1)/(a3-1) = 40/40/20 7900 1.72 Example 15

<Preparation of Resist Composition>

Examples 1 to 10 and Comparative Examples 1 to 5

Each of the components shown in Tables 2 and 3 was mixed and dissolved to prepare a resist composition of each Example.

TABLE 2 Component Component Component Component (A) (B) (D) (S) Example 1 (A1)-1 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 2 (A1)-2 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 3 (A1)-3 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 4 (A1)-4 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 5 (A1)-5 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 6 (A1)-6 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 7 (A1)-7 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 8 (A1)-8 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 9 (A1)-9 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400] Example 10  (A1)-10 (B)-1 (D)-1 (S)-1 [100] [20.0] [5.0] [6400]

TABLE 3 Component Component Component Component (A) (B) (D) (S) Comparative (A2)-1 (B)-1 (D)-1 (S)-1 Example 1 [100] [20.0] [5.0] [6400] Comparative (A2)-2 (B)-1 (D)-1 (S)-1 Example 2 [100] [20.0] [5.0] [6400] Comparative (A2)-3 (B)-1 (D)-1 (S)-1 Example 3 [100] [20.0] [5.0] [6400] Comparative (A2)-4 (B)-1 (D)-1 (S)-1 Example 4 [100] [20.0] [5.0] [6400] Comparative (A2)-5 (B)-1 (D)-1 (S)-1 Example 5 [100] [20.0] [5.0] [6400]

In Tables 2 and 3, each abbreviation has the following meaning. The numerical values in the brackets are blending amounts (parts by mass).

(A1)-1 to (A1)-10: the polymer compounds (A1-1) to (A1-10).

(A2)-1 to (A2)-5: the polymer compounds (A2-1) to (A2-5).

(B)-1: an acid generator composed of a compound represented by Chemical Formula (B-1).

(D)-1: an acid diffusion-controlling agent composed of a compound represented by Chemical Formula (D-1).

(S)-1: a mixed solvent of propylene glycol monomethyl ether acetate/propylene glycol monomethyl ether=60/40 (mass ratio)

<Formation of Resist Pattern>

The resist composition of each Example was applied onto an 8-inch silicon substrate which had been subjected to a hexamethyldisilazane (HMDS) treatment using a spinner, the coated wafer was subjected to a post-apply baking (PAB) treatment on a hot plate at a temperature of 110° C. for 60 seconds so that the coated wafer was dried to form a resist film having a film thickness of 30 nm.

Next, drawing (exposure) was performed on the resist film by using an electron beam lithography apparatus JEOL-JBX-9300FS (manufactured by JEOL Ltd.), with the target size being set to a 1:1 line-and-space pattern (hereinafter, referred to as an “LS pattern”) of a line width of 50 nm, at an accelerating voltage of 100 kV. Thereafter, a post-exposure baking (PEB) treatment was performed on the resist film at 110° C. for 60 seconds.

Subsequently, alkali development was performed at 23° C. for 60 seconds using a 2.38% by mass tetramethylammonium hydroxide (TMAH) aqueous solution “NMD-3” (trade name, manufactured by TOKYO OHKA KOGYO CO., LTD.).

Thereafter, rinsing was performed with pure water for 15 seconds.

As a result, a 1:1 LS pattern having a line width of 50 nm was formed.

[Evaluation of Optimum Exposure Amount (Eop)]

According to <Formation of resist pattern> described above, an optimum exposure amount Eop (μC/cm²) for forming the LS pattern having the target size was determined. The results are shown in Tables 4 and 5 as “Eop (μC/cm²)”.

[Evaluation of Exposure Margin]

In a case where the irradiation dose was decreased from the optimum exposure amount Eop (μC/cm²) so that the space dimension was decreased, the minimum exposure amount with which a pattern could be formed without causing defects such as scum and bridge was denoted by E0. On the other hand, in a case where the irradiation dose was increased from the optimum exposure amount Eop (μC/cm²) so that the space dimension was increased, the maximum exposure amount with which a pattern could be formed without causing defects such as collapse and disconnection was denoted by E1. The ratio (E1/E0) between the minimum exposure amount E0 and the maximum exposure amount E1 was shown in Tables 4 and 5 as the “Exposure margin”. It means that as the value of the exposure margin is larger, the performance of being able to form a pattern is higher even in a case where the irradiation dose varies.

TABLE 4 PAB PEB Eop Exposure (° C.) (° C.) [μC/cm²] margin Example 1 110 110 105 3.3 Example 2 110 110 95 3.5 Example 3 110 110 101 3.2 Example 4 110 110 87 3.0 Example 5 110 110 100 3.6 Example 6 110 110 93 3.8 Example 7 110 110 92 3.0 Example 8 110 110 81 3.2 Example 9 110 110 123 2.7 Example 10 110 110 109 2.6

TABLE 5 PAB PEB Eop Exposure (° C.) (° C.) [μC/cm²] margin Comparative 110 110 138 1.8 Example 1 Comparative 110 110 142 1.7 Example 2 Comparative 110 110 124 1.4 Example 3 Comparative 110 110 158 1.6 Example 4 Comparative 110 110 138 1.4 Example 5

As shown in Tables 4 and 5, it has been confirmed that high sensitivity can be obtained with the resist compositions of Examples while ensuring a wide exposure margin in the formation of the resist pattern as compared with the resist compositions of Comparative Examples.

The resins contained in the resist compositions of Comparative Examples 1, 4, and 5 contain a constitutional unit (a constitutional unit derived from a compound represented by Chemical Formula (a1-1) or (a1-3)) having a carbon-carbon double bond as an acid-dissociable group.

The acid-dissociable group contained in this constitutional unit has a lower deprotection reactivity than the acid-dissociable group of the constitutional unit (a01) contained in the resin (A1) of the resist composition of Examples.

For this reason, it is presumed that the resist compositions of Examples are excellent in sensitivity and exposure margin in the formation of the resist pattern as compared with the resist compositions of Comparative Examples 1, 4, and 5.

The resins contained in the resist compositions of Comparative Examples 2 and 3 contain a constitutional unit (a constitutional unit derived from a compound represented by Chemical Formula (a1-2)) having a carbon-carbon double bond as an acid-dissociable group.

The acid dissociation property of this constitutional unit is different from that of the acid-dissociable group of the constitutional unit (a01) contained in the resin (A1) of the resist composition of Examples, and thus the tertiary carbon atom that is bonded to the oxygen atom of the carbonyloxy group (C(═O)—O—) does not form a ring structure. For this reason, the resins contained in the resist compositions of Comparative Examples 2 and 3 have low rigidity and insufficient acid diffusion controllability.

Accordingly, it is presumed that the resist compositions of Examples are excellent in sensitivity and exposure margin in the formation of the resist pattern as compared with the resist compositions of Comparative Examples 2 and 3.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and is only limited by the scope of the appended claims. 

What is claimed is:
 1. A resist composition which generates an acid upon exposure and exhibits changed solubility in a developing solution under action of acid, the resist composition comprising: a resin component (A1) which exhibits changed solubility in a developing solution under action of acid, wherein the resin component (A1) has a constitutional unit (a01) derived from a compound represented by General Formula (a01-1):

wherein W⁰¹ represents a polymerizable group-containing group, C^(t) represents a tertiary carbon atom, X^(t) represents a group that forms a monocyclic or polycyclic alicyclic group together with C^(t), wherein part or all of hydrogen atoms which the monocyclic or polycyclic alicyclic group has may be substituted with a substituent, Ra¹ to Ra³ each independently represents a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or a hydrogen atom, or two or more of Ra¹ to Ra³ are bonded to each other to form an aliphatic ring, provided that not all of Ra¹ to Ra³ are hydrogen atoms, and n represents 0 or
 1. 2. The resist composition according to claim 1, wherein a proportion of the constitutional unit (a01) in the resin component (A1) is in a range of 30% to 70% by mole with respect to all constitutional units (100% by mole) constituting the resin component (A1).
 3. The resist composition according to claim 1, wherein in General Formula (a01-1), at least one of Ra² and Ra³ represents a hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, or two or more of Ra¹ to Ra³ are bonded to each other to form an aliphatic ring.
 4. A method of forming a resist pattern, comprising: forming a resist film on a support using the resist composition according to claim 1; exposing the resist film; and developing the exposed resist film to form a resist pattern.
 5. The method of forming a resist pattern according to claim 4, wherein the resist film is exposed with extreme ultraviolet (EUV) rays or electron beam (EB). 